package com.vivekjava;
import java.util.Scanner;
public class CBWinningScholarship {
public static void main(String args[]) {
Scanner cin = new Scanner(System.in);
int n = cin.nextInt(),
m = cin.nextInt(),//total discount
x = cin.nextInt(),//100% discount
y = cin.nextInt();//pay with discount amount
int si = 1, li = n, ans = 0;
while (si <= li) {
int mid = (si + li) / 2;
if (check(mid, n, m, x, y)) {
si = mid + 1;
ans = mid;
} else {
li = mid - 1;
}
}
System.out.print(ans);
}
static boolean check(int z, int n, int m, int x, int y) {
return z * x <= m + (n - z) * y;
}
}