#include <stdio.h>
#include <math.h>
 
typedef struct {
    double a;
    double b;
    double c;
} Triangle;
 
double calculateArea(Triangle t) {
    double s = (t.a + t.b + t.c) / 2;
    return sqrt(s * (s - t.a) * (s - t.b) * (s - t.c));
}
 
int main(void) {
    Triangle t;
 
    scanf("%lf", &t.a);
    scanf("%lf", &t.b);
    scanf("%lf", &t.c);
    printf("a:%lf,b:%lf,c:%lf\n",t.a,t.b,t.c);
 
    if (t.a + t.b > t.c && t.b + t.c > t.a && t.c + t.a > t.b) {
        double area = calculateArea(t);
        printf("三角形の面積: %lf\n", area);
    } else {
        printf("入力された値では三角形を形成できません。\n");
    }
    return 0;
}

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