90 pts 求调

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

double a, b, c, s;

int check (int a, int b, int c) {
	if (a <= 0 || b <= 0 || c <= 0) return 0;
	if (a + b > c && a + c > b && b + c > a) return 1;
	return 0;
}

signed main() {
	cin >> a >> b >> c;
	s = (a + b + c) / 2.0;
	if (check(a, b, c)) {
		double ans = 0;
		ans = sqrt(s * (s - a) * (s - b) * (s - c));
		cout << fixed << setprecision(2) << ans;
	} else {
		cout << "No solution.";
	}
    return 0;
}