#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long int;
clock_t tStart = clock();
void faltu() { cerr << endl; }
ll MOD = 1000000007;
ll BMOD = 1e18;
const double PI = acos(-1);
const double eps = 1e-9;
ll b_search(ll a[], ll l, ll r, ll x) {
  if (r >= l) {
    ll mid = l + (r - l);
    mid = mid >> 1;
    if (a[mid] == x) return mid;
    if (a[mid] > x) {
      return b_search(a, l, mid - 1, x);
    }
    return b_search(a, mid + 1, r, x);
  }
  return -1;
}
double deg(double x) { return ((180.0 * x) / PI); }
double rad(double x) { return ((x * (double)PI) / (180.0)); }
ll toInt(string s) {
  ll sm;
  stringstream ss(s);
  ss >> sm;
  return sm;
}
bool reversesort(const pair<ll, ll> &a, const pair<ll, ll> &b) {
  return (a.second > b.second);
}
bool isprime(ll n) {
  if (n == 2) return true;
  if (n % 2 == 0 || n % 3 == 0) return false;
  for (ll i = 5; i * i <= n; i += 6) {
    if (n % i == 0 || n % (i + 2) == 0) return false;
  }
  return true;
}
ll bigmod(ll a, ll b, ll M) {
  if (b == 0) return 1;
  if (b & 1) {
    return ((a % M) * (bigmod(a, b - 1, M) % M)) % M;
  } else {
    ll tmp = bigmod(a, b / 2, M) % M;
    return (tmp * tmp) % M;
  }
}
ll __gcd(ll a, ll b) {
  if (a == 0) return b;
  return __gcd(b % a, a);
}
bool lp(int y) {
  if (y % 400 == 0) return true;
  if (y % 400 != 0) {
    if (y % 100 != 0 and y % 4 == 0)
      return true;
    else
      return false;
  }
}
ll di_ch(double a, double b) { return fabs(a - b) < eps; }
int main() {
  ll t;
  cin >> t;
  ll r = 1;
  while (t--) {
    ld r;
    cin >> r;
    ld R = 2 * PI * r;
    cout << fixed << setprecision(20) << R << '\n';
  }
  return 0;
}
