#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef unsigned long long ull;

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll myRand(ll B) {
    return (ull)rng() % B;
}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    ll a,b,n,m; cin >> a >> b >> n >> m;
    ll L=0,R=1e18;
    R++;
    auto check=[](ll mid,ll a,ll b,ll n,ll m)->bool{
        if(a<mid and b<mid)return false;
        else if(a>=mid and b>=mid)return true;
        else if(a>b){
            a-=mid;
            return a/n+b>=mid;
        }
        else{
            b-=mid;
            return a+b/m>=mid;
        }
    };
    while(R-L>1){
        ll mid=(L+R)/2;
        if(check(mid,a,b,n,m)){
            L=mid;
        }
        else{
            R=mid;
        }
    }
    printf("%lld\n",L);
}