diff --git a/src/converter.rs b/src/converter.rs
index e53eabb..78c88b1 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))
     };
@@ -12,76 +12,49 @@ 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))
     }
 }
 
-pub fn from_int_to_oct(mut val: i32) -> String {
-    let mut s = String::new();
-    if val == 0 {
-        s += "0";
-    }
-    while val > 0 {
-        let rest = val % 8;
-        s += &rest.to_string();
-        val = val / 8;
-    }
+//to int
 
-    return s.chars().rev().collect();
-}
-
-pub fn from_int_to_hex(mut val: i32) -> String {
-    let mut s = String::new();
-    if val == 0 {
-        s += "0";
-    }
-    while val > 0 {
-        let rest = val % 16;
-        let to_string = rest.to_string();
-
-        s += match rest {
-            10 => "A",
-            11 => "B",
-            12 => "C",
-            13 => "D",
-            14 => "E",
-            15 => "F",
-            _ => &to_string
-        };
-        val = val / 16;
-    }
-
-    return s.chars().rev().collect();
-}
-
-pub fn from_int_to_bin(mut val: i32) -> String {
-    let mut s = String::new();
-    if val == 0 {
-        s += "0";
-    }
-    while val > 0 {
-        let rest = val % 2;
-        s += &rest.to_string();
-        val = val / 2;
-    }
-
-    return s.chars().rev().collect();
-}
-
-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> {
+pub fn from_dec_to_int(val: &str) -> Result<u128, String> {
     let mut dec = 0;
 
     for (i, c) in val.chars().rev().enumerate() {
-        let exp = i32::pow(8, i as u32);
 
+        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,
@@ -97,12 +70,16 @@ pub fn from_oct_to_int(val: &str) -> Result<i32, String> {
     return Ok(dec);
 }
 
-pub fn from_hex_to_int(val: &str) -> Result<i32, String> {
+pub fn from_hex_to_int(val: &str) -> Result<u128, String> {
     let mut dec = 0;
 
     for (i, c) in val.chars().rev().enumerate() {
-        let exp = i32::pow(16, i as u32);
 
+        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,
@@ -126,11 +103,16 @@ pub fn from_hex_to_int(val: &str) -> Result<i32, String> {
     return Ok(dec);
 }
 
-pub fn from_bin_to_int(val: &str) -> Result<i32, String> {
+pub fn from_bin_to_int(val: &str) -> Result<u128, String> {
     let mut dec = 0;
 
     for (i, c) in val.chars().rev().enumerate() {
-        let exp = i32::pow(2, i as u32);
+
+        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 {
@@ -139,4 +121,63 @@ pub fn from_bin_to_int(val: &str) -> Result<i32, String> {
     }
 
     return Ok(dec);
+}
+
+
+//FROM INT
+
+pub fn from_int_to_oct(mut val: u128) -> String {
+    let mut s = String::new();
+    if val == 0 {
+        s += "0";
+    }
+    while val > 0 {
+        let rest = val % 8;
+        s += &rest.to_string();
+        val = val / 8;
+    }
+
+    return s.chars().rev().collect();
+}
+
+pub fn from_int_to_hex(mut val: u128) -> String {
+    let mut s = String::new();
+    if val == 0 {
+        s += "0";
+    }
+    while val > 0 {
+        let rest = val % 16;
+        let to_string = rest.to_string();
+
+        s += match rest {
+            10 => "A",
+            11 => "B",
+            12 => "C",
+            13 => "D",
+            14 => "E",
+            15 => "F",
+            _ => &to_string
+        };
+        val = val / 16;
+    }
+
+    return s.chars().rev().collect();
+}
+
+pub fn from_int_to_bin(mut val: u128) -> String {
+    let mut s = String::new();
+    if val == 0 {
+        s += "0";
+    }
+    while val > 0 {
+        let rest = val % 2;
+        s += &rest.to_string();
+        val = val / 2;
+    }
+
+    return s.chars().rev().collect();
+}
+
+pub fn from_int_to_dec(val: u128) -> String {
+    val.to_string()
 }
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