#include <stdio.h>

int main()
{
    int n;
    scanf("%d", &n);
    int i, j;
    double sum = 0.0;
    for (i = 1; i <= n; i++)
    {
        int jiecheng = 1;
        for (j = 1; j <= i; j++)
        {
            jiecheng = jiecheng * j;
        }
        double sum1 = 1.0 / jiecheng;
        sum += sum1;
    }
    sum += 1;

    printf("%.10lf", sum);

    return 0;
}