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");
}