update usage in main.cpp

main.cpp

@@ -12,7 +12,7 @@ int main () {
      cin >> e;
      a.push_back (e);
   }
-  a = sort_custom(a);
+  a = sort_custom(a,0,a.size()-1);
   cout << endl;
   for(int i=0;i<a.size();i++){
     cout << a[i] << " ";