#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstdlib>
#include<vector>
#include<string>
#include<sstream>
#include<cmath>
#include<numeric>
#include<map>
#include<stack>
#include<queue>
using namespace std;
long long mod = 1e9 + 7;

int main(void) {
  int n; cin >> n;
  if(n == 0) cout << 0 << endl;
  else printf("%.10lf\n", 1.0/7);

  return 0;
}



// EOF