#include<bits/stdc++.h>
#define int long long
using namespace std;
int n;
double e = 1.0;
signed main () {
cin >> n;
int p = 1;
for (int i = 1; i <= n; i++) {
p *= i;
e += 1.0 / (p * 1.0);
}
cout << fixed << setprecision(10) << e << endl;
return 0;
}