#include<stdio.h>
int main()
{
	int a,b;
	scanf("%d%d",&a,&b);
	printf("%.2f", 3.1415926*2*a*(a+b));
	return 0;
}
/**************************************************************
	Problem: 1623
	User: admin
	Language: C
	Result: Accepted
	Time:16 ms
	Memory:1144 kb
****************************************************************/