#include<stdio.h>
void main()
{
	int r1,r2;
	double s,p=3.14;
	scanf("%d%d",&r1,&r2);
	s=p*r1*r1-p*r2*r2;
	printf("%.2f",s);
	
}
/**************************************************************
	Problem: 1338
	User: admin
	Language: C
	Result: Accepted
	Time:9 ms
	Memory:1144 kb
****************************************************************/