#include <iostream>

using namespace std;

int main() {
    int i = 1;
    int n;
    cin >> n;
    double sum = 0;
    int c = 1;
    while ( i <= n) {
        c = c*i;
        sum = sum + 1.0*1/c;
        i++;
    }
    cout << sum;
    return 0;
}