#include <bits/stdc++.h>

using namespace std;

int main()
{
	double sx, sy, gx, gy;

	cin >> sx >> sy >> gx >> gy;

	double x = (sy*gx + gy*sx) / (sy + gy);

	cout.precision(12);
	cout << x;

	return 0;
}
#include <iostream>
#include <string>
#include <cmath>
using namespace std;

int main() {

	float R, X, Y;
	cin >> R >> X >> Y;

	double dist = sqrt(X * X + Y * Y);
	int ans = 0;
	while (true) {
		ans++;
		if (R == dist) break;
		if (R < dist) dist -= R;
		if (R > dist) {
			ans += 1;
			break;
		}
	}

	cout << ans << endl;
	return 0;
}