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