#include<iostream>
using namespace std;
unsigned long long a,b,c,ans=0;
int main(){
	cin>>a>>b>>c;
	c=a+b;
	while(c>0){
		ans*=2;
		c=c-ans;
	}
	cout<<ans<<endl;
	return 0;
}
/*
n+(n-1)+.....+1<=a+b+c
big->n?

*/