#include <bits/stdc++.h>
using namespace std;
int main(){
  cout << fixed << setprecision(10);
  int k;
  cin >> k;
  double ans = 0;
  for (int i = 1; i <= 10; i++){
    double tmp = sin(k * i);
    for (int j = 0; j < i; j++){
      tmp /= i;
    }
    ans += tmp;
  }
  cout << ans << endl;
}