只有3个对的......

#include<bits/stdc++.h>
using namespace std;

int a[5];

int main() {
	cin >> a[1] >> a[2] >> a[3];
	sort(a + 1, a + 3 + 1);
	if (a[1] + a[2] > a[3]) {
		double s = (a[1] + a[2] + a[3]) / 2;
		double S = sqrt( 1.0 * s * (s - a[1]) * (s - a[2]) * (s - a[3]));
		printf("%.2lf", S);
	}
	else {
		cout << "No solution.";
	}
	return 0;
}