Lightoj 1178

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <iostream>
#include <stack>
#include <queue>
#include <vector>
#include <cmath>
#include <map>
#include <set>
#define ll long long
#define llu unsigned long long
using namespace std;
const int maxn = 100010;
const double eps = 1e-8;
const double PI  = acos(-1.0);

int main(){
int T; scanf("%d",&T);
for(int cas = 1; cas<=T; cas++){
double a,b,c,d;
scanf("%lf%lf%lf%lf",&a,&b,&c,&d);
double l = (b*b-d*d+(a-c)*(a-c))/(2*(a-c));
double h = sqrt(b*b-l*l);
printf("Case %d: %.9lf\n",cas,(a+c)*h/2);
}
return 0;
}