#include<stdio.h>
#include<math.h>
int main()
{
    float a,b,c,s,area,i;
    printf("Enter a b c");
    scanf("%f %f %f",&a,&b,&c);
    s=(a+b+c)/2;
    i=s(s-a)(s-b)(s-c);
    if(i<0)
        printf("error\n");
    else
        {
            area=sqrt(i);
            printf("The area is %f",area);
        }
         
    return 0;
}

谢谢