there are no errors. why?

#include <iostream.h>
int main()
{
  int i,j;
  cin >> i;

  j= abs(i)*(abs(i)+1)/2;
  if (i>=1) cout << j; else
  cout << (-j+1);
}

#include <iostream>   // <-- Problem was here
using namespace std;  // change it in your solution
int main()
{
int i,j;
cin >> i;

j= abs(i)*(abs(i)+1)/2;
if (i>=1) cout << j; else
cout << (-j+1);
}