压力！！！

#include<bits/stdc++.h>
using namespace std;
int main(){
    int n;
    double f = 1;
    cin>>n;
    long long b = 1;
    for(int i = 1;i <= n;i++){
        b *= i;
        if(i % 2 == 0){
            f += 1.0 / b;
        }else{
            f -= 1.0 / b;
        }
    }
    printf("%.8f",f);
    return 0;
}