求三角形面積

Problem Description

Input

Output

Example Input

1 2 2.5

Example Output

0.950

Hint

Author

參考程式碼

#include<stdio.h>
#include<math.h>
double f(double a,double b,double c)
{
    double s;
    double p;
    p = (a + b + c) / 2;
    s = sqrt(p * (p - a) * (p - b) * (p - c));
    return s;
}
int main()
{
    double a,b,c;
    double s;
    scanf("%lf%lf%lf",&a,&b,&c);
    s = f(a,b,c);
    printf("%.3lf",s);
    return 0;
}