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#include<bits/stdc++.h>
using namespace std;

typedef long long ll;

ll a,b,l,d1,a1,b1,ans;

int main(){

    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

    cin>>a>>b;
	for (ll i=40;i>=0;i--){
	    l=(1ll<<i);
	    d1=(l<<1);
	    a1=a/d1*l+max(0ll,a%d1-l);
	    b1=(b+1)/d1*l+max(0ll,(b+1)%d1-l);
        if((b1-a1)%2) ans+=l;
	}
	cout<<ans;

    return 0;
}

Measured memory_bytes: 256