#include<bits/stdc++.h>
using namespace std;

int main(){
  int64_t a,b,n,m; cin >> a >> b >> n >> m;
  
  if(a==b){
    cout << a << endl;
    return 0;
  }
  
  int64_t mini=min(a,b);
   if(a>b){
    for(int64_t i=0;min(a,b)==a;i++){
      a-=n;
      b++;
      mini=max(min(a,b),mini);
    }
   }
    
    else{
    for(int64_t i=0;min(a,b)==b;i++){
      b-=m;
      a++;
      mini=max(min(a,b),mini);
    }
  }
    
    cout << mini << endl;
}