#include <iostream>
#include <vector>
#include <cmath>
using namespace std;
bool canDo (vector<pair<int,int> > v, int x) {
if (x == 0) {
return true;
}
for (auto& p: v) {
while (p.first != 0 && (int)log2(p.first) == (int)log2(p.second)) {
int bit = log2(p.first);
p.first ^= (1 << bit), p.second ^= (1 << bit);
if (x & (1 << bit)) {
x ^= (1 << bit);
}
}
}
for (auto& p: v) {
if (p.second != 0 && (1 << (int)log2(p.second)) > x) {
return true;
}
}
int cntr = 0;
for (auto& p: v) {
if (p.second != 0) {
cntr += ((int)log2(p.second) == (int)log2(x));
}
}
if (cntr >= 2) {
return true;
}
for (auto& p: v) {
if (p.second != 0 && (int)log2(p.second) == (int)log2(x)) {
int bt = log2(p.second);
p.first = 0;
p.second -= (1 << bt);
x -= (1 << bt);
return canDo(v, x);
}
}
return false;
}
bool canDo (vector<vector<pair<int,int>>> &vec, int x) {
for (auto& v: vec) {
if (!canDo(v, x)) {
return false;
}
}
return true;
}
int find_best (vector<vector<pair<int,int>>> &vec) {
int tot = 0;
for (int i = 30; i >= 0; i--) {
if (canDo(vec, tot + (1 << i))) {
tot += (1 << i);
}
}
return tot;
}
int main() {
int n, m;
cin >> n >> m;
int tot[m];
for (int i = 0; i < m; i++) {
cin >> tot[i];
}
vector<vector<pair<int,int>>> vec;
for (int i = 0; i < m; i++) {
vec.emplace_back();
while (tot[i]--) {
pair<int,int> p;
cin >> p.first >> p.second;
vec.back().push_back(p);
}
}
cout << find_best(vec) << '\n';
return 0;
}
