// Page 294 - Programming Challenges problem #1.
#include 
using namespace std;

int main()
{
   int i, n, sum;

   cout << "Please enter a positive integer: ";
   cin >> n;

   i = 1;

   sum = 0;

   while (i <= n)
   {
      sum = sum + i;
      i = i + 1;
   }

   cout << "\nThe sum 1, 2, ..., " << n 
        << " is " << sum 
        << endl << endl;
}