#include <bits/stdc++.h> using namespace std; int main() { int n; cin >> n; double sum = 0.0; for (int i = 1; i <= n; i++) { if (i % 2 == 1) { sum += 1.0 / i; } else { sum -= 1.0 / i; } } cout << fixed << setprecision(4) << sum << endl; return 0; }