题解

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