#include <stdio.h>
double prob(int n)
{
    double k,o,sum;
    unsigned int i,j;
    k = 1;
    for (i = 2; i <= n; i++)
    {
        o = 1;
        for (j = 1; j <= i; j++) o = o / j;
        k = k + o;
    }
    return(k);
}
int main(void)
{
    int h;
    double l;
    scanf_s("%d", &h);
    l = prob(h);
    printf("%lf", l);
    return 0;
}