#include <iostream>

using namespace std;
int main()
{
  int n;
  int s;
  cout << "Wartosc danej N: ";
  cin >> n;
  if(n > 0){
      s = n*(n+1)/2;
      cout << "S wynosi " << s;
  }else{
      cout << "n < 1 ";
  }
  return 0;
}