#include <bits/stdc++.h>
using namespace std;
typedef double DB;
DB r1, r2, r, r12, r22;

/*{ self-adjasting simpson*/
DB func(DB x) {
	x = x * x;
	return sqrt(r12 - x) * sqrt(r22 - x);
}
DB simpson(DB a, DB b) {
	return (func(a) + 4 * func(a + (b - a) / 2) + func(b)) * (b - a) / 6;
}
DB asr(DB a, DB b, DB eps, DB A) {
	DB c = a + (b - a) / 2;
	DB l = simpson(a, c), r = simpson(c, b);
	if(fabs(l + r - A) <= eps * 15) return l + r + (l + r - A) / 15.0;
	return asr(a, c, eps / 2, l) + asr(c, b, eps / 2, r);
}
DB asr(DB a, DB b, DB eps) {
	return asr(a, b, eps, simpson(a, b));
}
/*} end*/


int main() {
	scanf("%lf%lf", &r1, &r2);
	r12 = r1 * r1, r22 = r2 * r2;
	r = min(r1, r2);
	printf("%.10lf\n", asr(0.00, r, 1e-8) * 8);
	return 0;
}