#include <bits/stdc++.h>
#define PI 2*acos(0)
using namespace std;
int main()
{
int n,tc,i,j;
char t[2];
cin>>tc;
while(tc--)
{
int a,b;
cin>>a;
if(getchar()=='\n')
{
printf("%.4lf\n", (2*a*a*PI)/16);
}
else
{
cin>>b;
printf("%.4lf\n", 2*a*b*PI);
}
}
return 0;
}
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