#include <stdio.h>
#include <math.h>
 
struct Triangle {
    double a;
    double b;
    double c;
};
 
int main(void) {
    struct Triangle tri;
    double s, area;
 
    if (scanf("%lf %lf %lf", &tri.a, &tri.b, &tri.c) != 3) {
        return 1;
    }
 
 
    s = (tri.a + tri.b + tri.c) / 2.0;
 
    area = sqrt(s * (s - tri.a) * (s - tri.b) * (s - tri.c));
 
    printf("a:%.0f\n", tri.a);
    printf("b:%.0f\n", tri.b);
    printf("c:%.0f\n", tri.c);
    printf("三角形の面積 : %f\n", area);
 
    return 0;
}
 

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