diff --git a/arithmetic_derivative.c b/arithmetic_derivative.c
index a8e5f8a..55db51f 100644
--- a/arithmetic_derivative.c
+++ b/arithmetic_derivative.c
@@ -1,57 +1,56 @@
-#define VERSION "0.10"
-#define N 100
-
 #include <stdio.h>
 
-int derive (int n);
-void split (int value, int *a, int *b);
+long long derive (long long n);
+void split (long long value, long long *a, long long *b);
 
 int main () {
-	int n, res;
-	int sgn;
-	char again;
-	do {
-		sgn = 1;
-		printf ("Enter an integer: ");
-		scanf ("%d", &n);
-		if (n < 0)
-			sgn = -1;
-		res = derive (sgn * n);
-		res = sgn * res;
-		printf ("The arithmetic derivative of %d is: %d", n, res);
-		getchar ();
-		printf ("\nAgain? [y/n] ");
-		scanf ("%c", &again);
-	} while (again != 'n');
-	printf ("\n\n\nversion: %s", VERSION);
+    long long n, res;
+    int sgn;
+    char again;
+    do {
+        sgn = 1;
+        printf ("Enter an integer: ");
+        scanf ("%lli", &n);
+        if (n < 0)
+            sgn = -1;
+        if ( sgn * n > 9999999999999999)
+            printf ("Warning! Number too big. The result could be wrong\n");
+        res = derive (sgn * n); // derive (abs (n))
+        res = sgn * res; // (-n)' = -(n')
+        printf ("The arithmetic derivative of %lli is: %lli", n, res);
+        getchar ();
+        printf ("\nAgain? [y/n] ");
+        scanf ("%c", &again);
+    } while (again != 'n');
 }
 
-int derive (int n){
-	int a = 1, b = 1;
-	switch (n) {
-		case 0:	return 1; break;
-		case 1: return 0; break;
-		default:
-			split (n, &a, &b);
-			if (b > 1){ // not a prime
-				n = derive (a) * b + a * derive (b);
-			} else {
-				n = 1;
-			}
-			return n; 
-			break;
-	}
+// if n=ab  (a and b > 1) -> n'=a'b + ab'
+long long derive (long long n){
+    long long a = 1, b = 1;
+    switch (n) {
+        case 0:	return 0; break; // 0' = 0
+        case 1: return 0; break; // 1' = 0;
+        default:
+            split (n, &a, &b); // n = a * b
+            if (b > 1) // if n is not a prime
+                n = derive (a) * b + a * derive (b);
+            else
+                n = 1; // if n is a prime
+            return n; 
+            break;
+    }
 }
 
-void split (int value, int *a, int *b) {
-	int i = 2;
-	int j = 0;
+// n = a * b
+void split (long long value, long long *a, long long *b) {
+	long long i = 2;
+	int stop = 0;
 	do {
         if (value % i == 0) {
 			*a = i;
 			*b = value / *a;
-			j++;
+			stop++;
 		}
 		i++;
-	} while (j == 0);
+	} while (stop == 0);
 }