#include "bits/stdc++.h"
using namespace std;
 
int main() {
  int A,B,C,D,res,can;
  cin >> A >> B >> C >> D;

  res=0,can=0;
  can = B / C; 
  
  if (A >= can){
    res = can;
  }
  else{
    res = A;
    B = C * A;
  }

  if (res+B <= D){
    cout << res << endl;
  }
  else{
    while(res+B >= D)
    {
      res -= 1;
      if(res<0){
        res = 0;
        break;
      }
      B -= C;
    }
    cout << res << endl;
  }


}