#include <stdio.h>
#include <math.h>
 
int main() {
    double a, b, c;
    double s, area;
 
    printf("3辺の長さを入力してください (a b c): ");
    scanf("%lf %lf %lf", &a, &b, &c);
 
    if (a + b > c && a + c > b && b + c > a) {
        s = (a + b + c) / 2;
 
        area = sqrt(s * (s - a) * (s - b) * (s - c));
 
        printf("三角形の面積は: %.2f\n", area);
    } else {
        printf("入力された3辺では三角形を作ることができません。\n");
    }
 
    return 0;
}
 

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