#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int pi = 3.14159265358979323846264338327;
void solve() {
  cout << setprecision(10) << endl;
  int r;
  cin >> r;
  cout << 2 * r * pi << endl;
}
int main() {
  int ___T;
  scanf("%d", &___T);
  for (int cs = 1; cs <= ___T; cs++) {
    solve();
  }
  return 0;
}
