题解

#include<iostream>
#include<cmath>
#include<cstdio>
using namespace std;
int main(){
    double a,b,c,d,e;
    cin>>a>>b>>c>>d>>e;
    double p=(a+b+e)/2,p2=(c+d+e)/2;
	printf("%.2f",sqrt(p*(p-a)*(p-b)*(p-e))+sqrt(p2*(p2-c)*(p2-d)*(p2-e)));
    return 0;
}