Tableta

#include <cstdio>
#include <algorithm>
#define LL long long int
using namespace std;

LL rec(LL l,LL c,int pas )
{
    if(pas==1)
        return (l+c)%2;
    else
    {
        LL mid=1<<(pas-1);
        if(l<=mid&&c<=mid)
            return rec(l,c,pas-1);
        else
            if(l<=mid&&c>mid)
                return rec(l,(c-mid),pas-1)+mid;
            else
                if(l>mid&&c<=mid)
                    return rec((l-mid ),c,pas-1)+mid;
                else
                    return rec((l-mid),(c-mid),pas-1);
    }
}

int main()
{
    freopen("tabela.in","r",stdin);
    freopen("tabela.out","w",stdout);
    LL a,b,dim,putere;
    dim=1;
    putere=0;
    scanf("%lld%lld",&a,&b);
    while(max(a,b)>=dim)
      dim*=2,++putere;
    printf("%lld",rec(a,b,putere));
    return 0;
}