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

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