题解

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