#include <stdio.h>
#include <math.h>
 
 
typedef struct {
    double a;
    double b;
    double c;
} triangle;
 
double s(triangle t) {
    double p = (t.a + t.b + t.c) / 2; 
    return sqrt(p * (p - t.a) * (p - t.b) * (p - t.c));  
}
 
int main() {
    triangle t; 
    scanf("%lf %lf %lf", &t.a, &t.b, &t.c);
    printf("a:%.0f\n", t.a);
    printf("b:%.0f\n", t.b);
    printf("c:%.0f\n", t.c);
    printf("三角形の面積:%.6f\n", s(t));
 
    return 0;
}
 
 
 
 
 
 

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