#include <iostream>
using namespace std;
int main(){
int n;
double e = 1,p;
cin >> n;
for (int i=1;i<=n;i++){
p = 1;
for(int j=1;j<=i;j++)
p = p * j;
e = e + 1/p;
}
printf("%.10f",e);
return 0;
}