#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <cstdlib>
using namespace std;

const double pi = atan(1) * 4;
double ans;

int main() {
	long long n, m;
	scanf("%lld %lld", &n, &m);
	for (long long i = 1; i < m; i++) {
		if (pi * i / (m * 1.00000) < 2) {
			for (long long u = 1; u <= n; u++) {
				for (long long v = 1; v <= n; v++) {
					long long minn = min(u, v), maxx = max(u, v);
					ans += maxx - minn + pi * i / (m * 1.00000) * minn;
				}
			}
		} else {
			for (long long u = 1; u <= n; u++) {
				for (long long v = 1; v <= n; v++)
					ans += u + v;
			}
		}
	}
	for (long long i = 1; i <= n; i++) {
		for (long long j = i + 1; j <= n; j++)
			ans += j - i;
	}
	ans *= (2 * m);
	double cnt = 0;
	for (long long i = 1; i <= n; i++) {
		for (long long j = 1; j <= n; j++)
			cnt += i + j;
	}
	ans += cnt * m; // 处理圆心角为 π时的情形。 
	if (m >= 2) { // m >= 2 时，多条直线在原点处相交产生一个交点。 
		for (long long i = 1; i <= 2 * m; i++) {
			for (long long j = 1; j <= n; j++) {
				ans += j;
			}
		}	
	}
	printf("%.10lf\n", ans);
	return 0;
}