#include <stdio.h>
double fact (int n);

int main()
{
    int i, n;
    double item, sum;
    while (scanf("%d", &n) != EOF)
    {
        item = 0;
        sum = 0;
        for (i = 0; i <= n; i++)
        {
            item = 1.0 / fact(i);
            sum = item + sum;
        }
        printf("%.8f\n", sum);
    }
    return 0;
}

double fact(int n)
{
    int i;
    double result;
    result = 1;
    for (i = 1; i <= n; i++)
        result = result*i;
    return result;
}