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#include<iostream>
 
using namespace std;
#define int long long
int R, B, x, y;
 
int cal(int k){
 
    int r=(R-k), b=(B-k);
    if(r<0||b<0) return -1;
    r=r/(x-1); b=b/(y-1);
    return r+b;
}
 
signed main(){
 
    cin>> R>> B>> x>> y;
 
    int l=0, h=1e18+1;
    // h=min(R, B)+1にすると、cal()の中でのr<0, b<0の判定が不要に
    while(h-l>1){
        int md=(l+h)/2;
        if(cal(md)>=md) l=md;
        else h=md;
    }
 
    printf("%lld\n", l);
 
    return 0;
}