/*No.804 野菜が苦手*/
import java.io.*;
public class No804{
	public static void main(String[] args) {
		try(BufferedReader input =new BufferedReader(new InputStreamReader(System.in))){
			String[]s_input=input.readLine().split(" ");
			byte ordered_vegetables=Byte.parseByte(s_input[0]);
			byte ordered_meat=Byte.parseByte(s_input[1]);
			byte multiple=Byte.parseByte(s_input[2]);
			byte capacity=Byte.parseByte(s_input[3]);
			while(ordered_vegetables*multiple>ordered_meat){
				ordered_vegetables--;
			}
			while(ordered_vegetables+ordered_meat>capacity){
				ordered_vegetables--;
				ordered_meat-=multiple;
			}
			System.out.println(ordered_vegetables);
		}catch(Exception e){
			e.printStackTrace();
		}
	}
}