#include <stdio.h>
#include <math.h>
 
typedef struct {
    double a;
    double b;
    double c;
} atai;
 
double menseki(atai t) {
    double p=(t.a+t.b+t.c)/2.0;
    return sqrt(p*(p-t.a)*(p-t.b)*(p-t.c));
}
 
int main(void) {
    atai t;
    double s;
 
    t.a=5;
    t.b=5;
    t.c=5;
 
    s=menseki(t);
 
    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 : %f\n", s);
 
    return 0;
}
 

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