https://ac.nowcoder.com/acm/contest/332/G

C++版本一

题解：

暴力肯定超时

如果【a，b】那么差值b-a的代表增量，这个增量的二进制位的多少代表【a，b】有几位二进制位有过变化，那么变化过的二进制位肯定是1.

/*
*@Author:   STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=100000+10;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
ll t,n,m,k,q;
ll ans,cnt,flag,temp;
int a[N];
char str;
int main()
{
#ifdef DEBUG
	freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
#endif

    //scanf("%d",&t);
    while(~scanf("%lld%lld",&n,&m)){
        temp=m-n;
        cnt=0;
        while(temp){
            temp/=2;
            cnt++;
        }
        n|=m;
        n|=(ll)pow(2,cnt)-1;
        cout << n << endl;
    }
    //cout << "Hello world!" << endl;
    return 0;
}