#include using namespace std; int main() { int n; cin >> n; double s = 0; if (n % 2 == 0) { for (int i = 2; i <= n; i = i + 2) s += 1.0 / i; } else { for (int i = 1; i <= n; i = i + 2) s += 1.0 / i; } cout << s << endl; return 0; }