added ggT function to get the result

src/ggT/main.c

@@ -6,6 +6,7 @@ int main(){
     printf("add two numbers:\n");
     int firstNum = usergetd("first number: ", 0, NULL);
     int secondNum = usergetd("second number: ", 0, NULL);
+    int result = ggT(firstNum, secondNum);
 
     return 0;
 }