diff --git a/src/converter.rs b/src/converter.rs
index 78c88b1..e53eabb 100644
--- a/src/converter.rs
+++ b/src/converter.rs
@@ -2,7 +2,7 @@ pub fn convert(from: &str, to: &str, val: &str) -> Result<String, String> {
     let int_value = match from {
         "b" => from_bin_to_int(val)?,
         "o" => from_oct_to_int(val)?,
-        "d" => from_dec_to_int(val)?,
+        "d" => from_dec_to_int(val),
         "h" => from_hex_to_int(val)?,
         _ => return Err(format!("Not a valid system: {}", from))
     };
@@ -12,121 +12,11 @@ pub fn convert(from: &str, to: &str, val: &str) -> Result<String, String> {
         "o" => Ok(from_int_to_oct(int_value)),
         "d" => Ok(from_int_to_dec(int_value)),
         "h" => Ok(from_int_to_hex(int_value)),
-        _ => Err(format!("Not a valid system: {}", from))
+        _ =>Err(format!("Not a valid system: {}", from))
     }
 }
 
-//to int
-
-pub fn from_dec_to_int(val: &str) -> Result<u128, String> {
-    let mut dec = 0;
-
-    for (i, c) in val.chars().rev().enumerate() {
-
-        if dec > (u128::MAX / 10) {
-            return Err(format!("Number too big: {}", val));
-        }
-
-        let exp = u128::pow(10, i as u32);
-        dec += exp * match c.to_ascii_lowercase() {
-            '0' => 0,
-            '1' => 1,
-            '2' => 2,
-            '3' => 3,
-            '4' => 4,
-            '5' => 5,
-            '6' => 6,
-            '7' => 7,
-            '8' => 8,
-            '9' => 9,
-            _ => return Err(format!("Not a valid decimal number: {} at char {}: {}", val, i, c))
-        };
-    }
-    return Ok(dec);
-}
-
-pub fn from_oct_to_int(val: &str) -> Result<u128, String> {
-    let mut dec = 0;
-
-    for (i, c) in val.chars().rev().enumerate() {
-
-        if dec > (u128::MAX / 8) {
-            return Err(format!("Number too big: {}", val));
-        }
-
-        let exp = u128::pow(8, i as u32);
-        dec += exp * match c.to_ascii_lowercase() {
-            '0' => 0,
-            '1' => 1,
-            '2' => 2,
-            '3' => 3,
-            '4' => 4,
-            '5' => 5,
-            '6' => 6,
-            '7' => 7,
-            _ => return Err(format!("Not a valid octal number: {} at char {}: {}", val, i, c))
-        };
-    }
-    return Ok(dec);
-}
-
-pub fn from_hex_to_int(val: &str) -> Result<u128, String> {
-    let mut dec = 0;
-
-    for (i, c) in val.chars().rev().enumerate() {
-
-        if dec > (u128::MAX / 16) {
-            return Err(format!("Number too big: {}", val));
-        }
-
-        let exp = u128::pow(16, i as u32);
-        dec += exp * match c.to_ascii_lowercase() {
-            '0' => 0,
-            '1' => 1,
-            '2' => 2,
-            '3' => 3,
-            '4' => 4,
-            '5' => 5,
-            '6' => 6,
-            '7' => 7,
-            '8' => 8,
-            '9' => 9,
-            'a' => 10,
-            'b' => 11,
-            'c' => 12,
-            'd' => 13,
-            'e' => 14,
-            'f' => 15,
-            _ => return Err(format!("Not a valid hex number: {} at char {}: {}", val, i, c))
-        };
-    }
-    return Ok(dec);
-}
-
-pub fn from_bin_to_int(val: &str) -> Result<u128, String> {
-    let mut dec = 0;
-
-    for (i, c) in val.chars().rev().enumerate() {
-
-        if dec > (u128::MAX / 2) {
-            return Err(format!("Number too big: {}", val));
-        }
-
-        let exp = u128::pow(2, i as u32);
-        if c == '1' {
-            dec += exp;
-        } else if c == '0' {} else {
-            return Err(format!("Not a valid binary number: {} at char {}: {}", val, i, c));
-        }
-    }
-
-    return Ok(dec);
-}
-
-
-//FROM INT
-
-pub fn from_int_to_oct(mut val: u128) -> String {
+pub fn from_int_to_oct(mut val: i32) -> String {
     let mut s = String::new();
     if val == 0 {
         s += "0";
@@ -140,7 +30,7 @@ pub fn from_int_to_oct(mut val: u128) -> String {
     return s.chars().rev().collect();
 }
 
-pub fn from_int_to_hex(mut val: u128) -> String {
+pub fn from_int_to_hex(mut val: i32) -> String {
     let mut s = String::new();
     if val == 0 {
         s += "0";
@@ -164,7 +54,7 @@ pub fn from_int_to_hex(mut val: u128) -> String {
     return s.chars().rev().collect();
 }
 
-pub fn from_int_to_bin(mut val: u128) -> String {
+pub fn from_int_to_bin(mut val: i32) -> String {
     let mut s = String::new();
     if val == 0 {
         s += "0";
@@ -178,6 +68,75 @@ pub fn from_int_to_bin(mut val: u128) -> String {
     return s.chars().rev().collect();
 }
 
-pub fn from_int_to_dec(val: u128) -> String {
+pub fn from_int_to_dec(val: i32) -> String {
     val.to_string()
+}
+
+pub fn from_dec_to_int(val: &str) -> i32 {
+    val.parse().expect("Not a valid decimal number")
+}
+
+pub fn from_oct_to_int(val: &str) -> Result<i32, String> {
+    let mut dec = 0;
+
+    for (i, c) in val.chars().rev().enumerate() {
+        let exp = i32::pow(8, i as u32);
+
+        dec += exp * match c.to_ascii_lowercase() {
+            '0' => 0,
+            '1' => 1,
+            '2' => 2,
+            '3' => 3,
+            '4' => 4,
+            '5' => 5,
+            '6' => 6,
+            '7' => 7,
+            _ => return Err(format!("Not a valid octal number: {} at char {}: {}", val, i, c))
+        };
+    }
+    return Ok(dec);
+}
+
+pub fn from_hex_to_int(val: &str) -> Result<i32, String> {
+    let mut dec = 0;
+
+    for (i, c) in val.chars().rev().enumerate() {
+        let exp = i32::pow(16, i as u32);
+
+        dec += exp * match c.to_ascii_lowercase() {
+            '0' => 0,
+            '1' => 1,
+            '2' => 2,
+            '3' => 3,
+            '4' => 4,
+            '5' => 5,
+            '6' => 6,
+            '7' => 7,
+            '8' => 8,
+            '9' => 9,
+            'a' => 10,
+            'b' => 11,
+            'c' => 12,
+            'd' => 13,
+            'e' => 14,
+            'f' => 15,
+            _ => return Err(format!("Not a valid hex number: {} at char {}: {}", val, i, c))
+        };
+    }
+    return Ok(dec);
+}
+
+pub fn from_bin_to_int(val: &str) -> Result<i32, String> {
+    let mut dec = 0;
+
+    for (i, c) in val.chars().rev().enumerate() {
+        let exp = i32::pow(2, i as u32);
+        if c == '1' {
+            dec += exp;
+        } else if c == '0' {} else {
+            return Err(format!("Not a valid binary number: {} at char {}: {}", val, i, c));
+        }
+    }
+
+    return Ok(dec);
 }
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