#include <stdio.h>
#include <math.h>
 
struct Triangle {
    double a;
    double b;
    double c;
};
 
int main(void) {
    struct Triangle x;
    double d, s;
 
    x.a = 5;
    x.b = 5;
    x.c = 5;
 
    d = (x.a + x.b + x.c) / 2.0;
 
    s = sqrt(d * (d - x.a) * (d - x.b) * (d - x.c));
 
    printf("a:%d\n", (int)x.a);
    printf("b:%d\n", (int)x.b);
    printf("c:%d\n", (int)x.c);
    printf("三角形の面積:%f\n", s);
 
    return 0;
}

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