cf 339D

#include<bits/stdc++.h>

using namespace std;

long long n, i, tree[9999999];

void ans(int id)
{
    int lvl = 1;
    while(id > 0)
    {
        if(lvl % 2 == 1) tree[id] = tree[id*2] | tree[id*2 + 1];
        else tree[id] = tree[id*2] ^ tree[id*2 + 1];
        lvl++;
        id /= 2;
    }
}

int main()
{
    long long q;
    cin >> n >> q;
    n = 1 << n;
    //printf("n %lld\n", n);
    long long x;
    for(i = n; i < 2*n; i++)
    {
        cin >> tree[i];
        ans(i/2);
    }

    while(q--)
    {
        long long p, b;
        cin >> p >> b;
        tree[p+n-1] = b;
        ans((p+n-1)/2);
        cout << tree[1] << endl;
    }

}