#line 2 "/home/defineprogram/Desktop/Library/template/template.cpp"
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define rep(i, n) for (int i = 0; i < n; i++)
#define REP(i, n) for (int i = 1; i < n; i++)
#define rev(i, n) for (int i = n - 1; i >= 0; i--)
#define REV(i, n) for (int i = n - 1; i > 0; i--)
#define all(v) v.begin(), v.end()
#define PL pair<ll, ll>
#define PI pair<int,int>
#define len(s) (int)s.size()

template <class T, class U>
inline bool chmin(T &a, U b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template <class T, class U>
inline bool chmax(T &a, U b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
constexpr ll inf = 3e18;
#line 2 "main.cpp"

int main() {
    cin.tie(0); ios::sync_with_stdio(false);
    ll A,B,N,M;
    cin>>A>>B>>N>>M;
    ll ok=0,ng=inf;
    while(ng-ok>1){
        ll mid=(ok+ng)/2;
        ll nA=A,nB=B;
        nB+=(A-mid)/N;
        nA+=(B-mid)/M;
        if(nA>=mid&&nB>=mid)ok=mid;
        else ng=mid;
    }
    cout<<ok<<endl;
}