1296.cpp

// Ivan Carvalho
// Solution to https://www.beecrowd.com.br/judge/problems/view/1296
#include <cmath>
using namespace std;
int main() {
    double m1, m2, m3;
    while (scanf("%lf %lf %lf", &m1, &m2, &m3) != EOF) {
        m1 *= m1;
        m2 *= m2;
        m3 *= m3;
        double total = 4 * (m1 + m2 + m3) / 3.0;
        double a = (2 * total - 4 * m1) / 3.0;
        double b = (2 * total - 4 * m2) / 3.0;
        double c = (2 * total - 4 * m3) / 3.0;
        if (a <= 0 || b <= 0 || c <= 0) {
            printf("-1.000\n");
            continue;
        }
        a = sqrt(a);
        b = sqrt(b);
        c = sqrt(c);
        if (a < b + c && b < a + c && c < a + b) {
            double p = (a + b + c) * 0.5;
            double area = p * (p - a) * (p - b) * (p - c);
            printf("%.3lf\n", sqrt(area));
        } else {
            printf("-1.000\n");
        }
    }
    return 0;
}