poj 1517 u Calculate e

#include <iostream>#include <cstdio>using namespace std;int main(){    cout << "n" << " e" << endl;    cout << "- -----------" << endl;    for (int i = 0; i <= 9; i++)    {        if (i == 0)           cout << i << " " << 1 << endl;        else if (i == 1)           cout << i << " " << 2 << endl;        else if (i == 2)           cout << i << " " << 2.5 << endl;        else         {             double sum = 1, ans = 0;             for (int j = 1; j <= i; j++)             {                  sum *= j;                  ans += 1 * 1.0 / sum * 1.0;             }             printf("%d %.9lf\n", i, ans + 1);        }    }        system("pause");}