import java.io.*;
import java.util.*;

public class Solution {

    public static void main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
        int n,c,u,s;
        Scanner sc=new Scanner(System.in);
        n=sc.nextInt();
        c=sc.nextInt();
        u=sc.nextInt();
        s=sc.nextInt();

        System.out.println(getMaxPlayers(n,c,u,s));

    }

    static int getMaxPlayers(int n,int c,int u,int s){
        int m=0;
        int i;
        int currentc=c;
        int t;
        if (c>=n*u) return n;
        for(t=0;t<=n;t++){
            if(s*t+c<=(n-t)*u) return (n-t);
        }
        return t;
    }
}