#include<bits/stdc++.h>
using namespace std; 
const int N=1e3+3;
int n,k,v[N],w[N],ans=4e4;
int main(){
    freopen("bag.in","r",stdin);
    freopen("bag.out","w",stdout);
	cin>>n>>k;
	for(int i=1;i<=n;i++) cin>>v[i]>>w[i];
	for(ans=4e4;ans>0;ans--){
		int t=0x7fffffff;
		for(int i=1;i<=n;i++){
			if((ans & w[i]) == ans){
				ans &= w[i];
				t &= v[i];
			}
		}
		if(t<=k){
			cout<<ans;
			return 0;
		}
	}
	cout<<ans;
	return 0;
}