求调

#include<cstdio>
#include<cmath>
using namespace std;
int main()
{
    double a,b,c,p,s;
    p = (a + b + c)/2.0;
    s = sqrt (p* (p - a)*(p - b)*(p - c));
    scanf("%lf %lf %lf",&a,&b,&c);
    printf("%.1lf",s);
    return 0;
}