#include <iostream>
#include <cmath>
#include <bits/stdc++.h>

#define int long long

long double pi = acos(-1);
constexpr int mod = 0x3b800001;
int n, m;

using namespace std;

signed main() {
  std::cin.tie(nullptr)->sync_with_stdio(false);
  std::cin >> n >> m;
  if (m == 1) {
    long double ans = 0;
    for (int i = 1, j = n + n; i <= n + n; ++i, --j) {
      ans += i * j;
    }
    for (int i = 1; i <= n; ++i) {
      ans -= i + i;
    }
    std::cout << std::fixed << std::setprecision(10) << ans << '\n';
    return 0;
  }
  int ans = 0;
  int s1 = 0, s2 = 0;
  for (int i = 1; i <= n; ++i) {
    s1 = (s1 + 1LL * i * (n - i + 1));
    s1 = (s1 + 1LL * i * (n - i));
    s2 = (s2 + 1LL * i * i);
    s2 = (s2 + 1LL * i * (i - 1));
  }
  int ans_pi = 0, ans_1 = 0;
  for (int i = 1; i < m; ++i) {
    if (pi * i > 2 * m) {
      ans_1 = (ans_1 + 1LL * s1 * (m + m));
      ans_1 = (ans_1 + 1LL * s2 * (m + m));
    } else {
      ans_1 = (ans_1 - 1LL * s1 * (m + m));
      ans_1 = (ans_1 + 1LL * s2 * (m + m));
      ans_pi = (ans_pi + 2LL * i * s1);
    }
  }
  for (int i = 1, j = n + n; i <= n + n; ++i, --j) {
    ans_1 = (ans_1 + 1LL * m * i * j);
  }
//   std::cout << ans_pi << ' ' << ans_1 << '\n';
  std::cout << fixed << setprecision(10) << ans_pi * pi + ans_1 << '\n';
  return 0;
}