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


signed main() {
  int A, B, C, D;
  cin >> A >> B >> C >> D;
  
  int ans = 0;
  for( int yasai = 0; yasai <= A; yasai++ ){
    for( int niku = yasai*C; niku <= B; niku+=C ){
      if( yasai + niku <= D ) ans = yasai;
    }
  }
  cout << ans << endl;
    
}