#include <bits/stdc++.h>
using namespace std;
long long int in() {
  long long int n;
  cin >> n;
  return n;
}
signed main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long int t = in();
  while (t--) {
    long double n;
    cin >> n;
    n = n * 1.000000000;
    long double ans, pi = 3.14159265358979323846264;
    ans = 2.0000000000000 * pi * n * 1.000000000;
    cout << ans << "\n";
  }
  return 0;
}
