#include <iostream>
using namespace std;
int main(){
int n;
double sum = 0;
cin >> n;
for (int i=1;i<=n;i++){
if(i%2==1)
sum = sum + 1.0d/i;
else
sum = sum - 1.0d/i;
}
printf("%.4f",sum);
return 0;
}