#include <bits/stdc++.h>
#define NIL (-1)
#define ll long long
using namespace std;
const int64_t MOD = 1e9 + 7;
const int INF = INT_MAX;
const double PI = acos(-1.0);

int main() {
	ll A, B , N, M;
	cin >> A >> B >> N >> M;

	if (A > B) {
		ll dif = A - B;
		ll ans = 0;
		ll c = dif / (N+1);
		ans = max(ans, min(dif - N * c, c));
		c++;
		ans = max(ans, min(dif - N * c, c)); \
			cout << ans+B << endl;
	}
	else if (A<B) {
		ll dif = B - A;
		ll ans = 0;
		ll c = dif / (M+1);
		ans = max(ans, min(dif - M * c, c));
		c++;
		ans = max(ans, min(dif - M * c, c)); \
			cout << ans+A << endl;
	}
	else {
		cout << A << endl;
	}

	return 0;
}