#2869
#include <bits/stdc++.h>

using namespace std;

long long DivImp(long long l, long long c, long long cadran)
{
  if(cadran == 1) return 0;
  if(l <= cadran / 2 && c <= cadran / 2)
    return DivImp(l, c, cadran/2);
  else if(l > cadran / 2 && c > cadran / 2)
    return DivImp(l-cadran / 2, c - cadran / 2, cadran/2);
  else if(l <= cadran / 2 && c > cadran / 2)
        return DivImp(l, c-cadran/2, cadran/2) + cadran/2;
    else
        return DivImp(l-cadran/2, c, cadran/2) + cadran/2;

}
int main()
{
    ifstream fin("tabela.in");
    ofstream fout("tabela.out");

    long long l, c, l2, c2, cadran;
    fin >> l >> c;

    l2 = (long long)1 << ((long long)log2((double)l-1) + 1);
    c2 = (long long)1 << ((long long)log2((double)c-1) + 1);
    cadran = max(l2, c2);

    fout << DivImp(l, c, cadran);

    return 0;
}
/**cin >> a >> b;
cout << (a-1)^(b-1);


*/