package main

import . "fmt"


func main() {
	var n, m int
	Scan(&n,&m)
	
	ans := 0
	x := 0
	for i := 30; i >= 0; i-- {
		t := x + (1<<i)
		if t > m {
			continue
		}
		s, c := 0, 0
		for t > 1 {
			s += t
			c++
			if t % 2 == 0 {
				t /= 2
			} else {
				t = (t+1)/2
			}
		}
		if n - c < 1 {
			continue
		}
		x = x + (1<<i)
		ans = max(ans, s+n-c)
	}
	Println(ans)
}