#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using ull = unsigned long long;
using db = double;

#define For(i, j, k) for (int i = (j); i <= (k); i++)
#define ForDown(i, j, k) for (int i = (j); i >= (k); i--)

namespace {
ll qpow(ll x, ull y, ll mod) {
  ll ans = 1;
  while (y) {
    if (y & 1)
      (ans *= x) %= mod;
    (x *= x) %= mod, y >>= 1;
  }
  return ans;
}
const db pi = acos(-1);
int n, m;
void Main() {
  cin.tie(0)->sync_with_stdio(0);
  cin >> n >> m;
  if (m == 1) {
    ll ans = 0;
    For(i, 1, n)
      ans += (n - i + 1) * (n + i - 1);
    ans *= 2;
    cout << ans << '\n';
    return;
  }
  ll s1 = 0, s2 = 1;
  For(i, 1, m - 1) {
    if (i * pi > 2 * m) {
      s2 += 2;
    } else {
      s1 += i * 2;
    }
  }
  s2 *= m;
  ll ans1 = 0, ans2 = 0;
  For(i, 1, n) {
    ans2 += (ll(n - i + 1) * m * 2) * ((ll(i - 1) * m * 2 + 1));
    ll qwq = (n - i) * 2 + 1;
    ans1 += qwq * s1 * i;
    ans2 += qwq * s2 * 2 * i;
  }
  cout << fixed << setprecision(7) << ans1 *pi + ans2 << '\n';
}
}

int main() { return Main(), 0; }