给定4根长度的线段，求组成四边形的最大面积

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cstdlib>
using namespace std;
typedef long long ll;
double a[10];
int main(){
    ll t;
    scanf("%lld",&t);
    ll i;
    for(i=1;i<=t;i++){
        scanf("%lf%lf%lf%lf",a,a+1,a+2,a+3);
        sort(a,a+4);
        if(a[3]>=a[0]+a[1]+a[2]){
            printf("Case %lld: -1\n",i);
            continue;
        }
        double p=(a[1]+a[2]+a[3]+a[0])/2;
        double s=sqrt((p-a[0])*(p-a[1])*(p-a[2])*(p-a[3]));
        printf("Case %lld: %.6lf\n",i,s);
        
    }
}