#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx")
#include <bits/stdc++.h>

int main() {
  long double n;
  std::cin >> n;
  long double ans = 0.0;
  if(n < 0.0000000000000001) {
    ans += 1.0;
    n += 1.0;
  }
  for(int i = 0;i < 100000000;++i) {
    long double tmp = sin(n + i) / (n + i);
    ans += tmp * tmp;
  }
  std::cout << ans << std::endl;
  return 0;
}