可以使用（#define _USE_MATH_DEFINES），也可以用#派#:3.1415926535897932384626433832795028841971693993751058209749445923078164062

#define _USE_MATH_DEFINES
#include<bits/stdc++.h>
using namespace std;
int main(){
	long long x,y,t;
	cin>>x>>y;
	t=((x*x+y*y)*M_PI/*3.1415926535897932384626433832795028841971693993751058209749445923078164062*//100);
	cout<<t;
	return 0;
}