#include <stdio.h>
#include <math.h>
struct hen{
double a;
double b;
double c;
}length;
int main(void) {
// your code goes here
double S,s;
s=(length.a+length.b+length.c)/2;
S=s*(s-length.a)*(s-length.b)*(s-length.c);
return 0;
}
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