package main

import (
	"fmt"
)

func main() {
	var n, x, a, b int64
	fmt.Scan(&n, &x, &a, &b)
	max := pow(2, n)/2 - 1

	hp1 := x
	attack := 0
	for hp1 > 0 {
		hp1 -= a
		attack++
	}

	hp2 := x
	recovery := 0
	for hp2 <= max {
		hp2 += b
		recovery++
	}
	
	if attack < recovery {
		fmt.Println(attack)
	} else {
		fmt.Println(recovery)
	}
}

func pow(n, k int64) int64 {
	r := int64(1)
	for ; k > 0; k >>= 1 {
		if k&1 == 1 {
			r *= n
		}
		n *= n
	}
	return r
}