774G - Perfectionist Arkadiy - CodeForces Solution

#include<bits/stdc++.h>
#include<array>
//#define x first
#define y second
using namespace std;
typedef long long ll;
const int N = 200005;
const int mod = 998244353;
typedef pair<int, int> pii;
int gcd(int a, int b) {
	if (b == 0) return a;
	return gcd(b, a % b);
}
const double eps = 1e-6;
int main() {
	int a, h, w;
	cin >> a >> h >> w;
	if (a > h || a > w) {
		cout << -1 << endl;
		return 0;
	}
	double g = gcd(a + h, w + a);
	double y = floor(g * 1.0 / a);
	if ( abs(y) <= eps) {
		cout << -1 << endl;
	}
	else {
		double x = g / y - a;
		printf("%.6llf\n", x);
	}
	return 0;
}