不知道該說些什麼。。。

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
using namespace std;
#define ll long long
#define inf 0x3f3f3f3f
#define N 110
inline char gc(){
    static char buf[1<<16],*S,*T;
    if(S==T){T=(S=buf)+fread(buf,1,1<<16,stdin);if
 
(T==S) return EOF;}
    return *S++;
}
inline ll read(){
    ll x=0,f=1;char ch=gc();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=gc();}
    while(ch>='0'&&ch<='9') x=x*10+ch-'0',ch=gc();
    return x*f;
}
ll l,r;
int main(){
//  freopen("a.in","r",stdin);
    l=read();r=read();int x=60
 
;
    while(x>=0){
        if((r>>x&1)&&!((l>>x&1))) break;--x;
    }printf("%I64d\n",(1LL<<x+1)-1);return 0;
}