代码：

#include<bits/stdc++.h>
using namespace std;
int main()
{
	double a,b,c,p,ans;
	cin>>a>>b>>c;
	p = (a + b + c) / 2;
	ans = sqrt(p * (p - a) * (p - b) * (p - c));
	printf("%.1llf",ans);
	return 0;
} 

测试点一： 123.22 77.88 150.23 我的answer: 4786.8 题中answer: 4786.8

~~???????????~~求大佬指点