#include <bits/stdc++.h> using namespace std; using ll = long long; template<class T> bool cmin(T &i, T j) { return i > j ? i=j,true:false; } template<class T> bool cmax(T &i, T j) { return i < j ? i=j,true:false; } mt19937 mrand(chrono::steady_clock::now().time_since_epoch().count()); uniform_int_distribution<int> ui(0, 1 << 30); int rng() { return ui(mrand); } constexpr int LOG = 30; int main() { ios_base::sync_with_stdio(false); cin.tie(nullptr); int n,m; cin >> n >> m; vector<int> v(m); for (int &x: v) cin >> x; vector<array<int,2>> ranges(n); for (auto &[a,b]: ranges) cin >> a >> b; vector<vector<array<int,2>>> groups(m); for (int i = 0, j = 0, t = 0; i < n; i++) { if (j == v[t]) j = 0,t++; groups[t].push_back(ranges[i]); j++; } int res = 0; auto can_do = [&](vector<array<int,2>> w,int x) { for (int bit = LOG; bit >= 0; bit--) { // invariante: gli [a,b] sono contenuti in [0,2^(bit + 1) - 1] vector<int> ones,zeros; for (int i = 0; i < w.size(); i++) { auto [a,b] = w[i]; if (b == (1LL << (bit + 1)) - 1) return true; if ((a >> bit) & 1) { ones.push_back(i); } else if (b >= (1 << bit)) { zeros.push_back(i); } } if (zeros.size() >= 2 || (zeros.size() >= 1 && ones.size() >= 1)) return true; if (!((x >> bit) & 1)) { if (zeros.size() >= 1) return true; for (int idx: ones) { w[idx][0] -= 1 << bit; w[idx][1] -= 1 << bit; } continue; } // zeros.size() è 0 o 1; se è 1, è l'unico candidato if (zeros.size() == 1) { w[zeros[0]][1] -= 1 << bit; w[zeros[0]][0] = 0; } else { if (ones.empty()) return false; for (int idx: ones) { w[idx][0] -= 1 << bit; w[idx][1] -= 1 << bit; } } } return true; }; auto can = [&](int x) { for (auto w: groups) if (!can_do(w,x)) return false; return true; }; for (int bit = LOG; bit >= 0; bit--) { if (can(res | (1 << bit))) res |= (1 << bit); } cout << res << "\n"; }