#include <stdio.h>
#include <math.h>
 
struct Triangle{
	double a;
	double b;
	double c;
}tri;
 
int main(void)
{
	scanf("%lf %lf %lf ", &tri.a, &tri.b, &tri.c);
 
	double p = (tri.a + tri.b + tri.c) / 2.0;
    double s = sqrt(p * (p - tri.a) * (p - tri.b) * (p - tri.c));
 
 
    printf("a: %.0lf\n", tri.a);
    printf("b: %.0lf\n", tri.b);
    printf("c: %.0lf\n", tri.c);
    printf("三角形の面積：%.6lf\n", s);
 
	return 0;
}
 

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