#include<bits/stdc++.h>
#include<atcoder/all>
using namespace std;
using namespace atcoder;

typedef modint998244353 mint;
typedef long long ll;

// makediv
vector<ll> makediv(ll n){
	vector<ll> ld, ud;
	for (ll i=1; i*i<=n; i++){
		if (n%i == 0){
			ld.push_back(i);
			if (i != n/i){
				ud.push_back(n/i);
			}
		}
	}
	reverse(ud.begin(), ud.end());
	ld.insert(ld.end(), ud.begin(), ud.end());
	return ld;
}
// -----

int main(){
	int n,m; cin >> n >> m;
	vector<ll> a(n);
	vector<ll> a2(n);
	vector<ll> b(m);
	vector<ll> b2(m);
	for (int i=0; i<n; i++){
		cin >> a[i];
		a2[i] = a[i] * a[i];
	}
	for (int i=0; i<m; i++){
		cin >> b[i];
		b2[i] = b[i] * b[i];
	}

	if (a[0] != 1 || b[0] != 1){
		cout << 1 << endl;
		return 0;
	}

	vector<bool> c(40000);
	for (int i=0; i<n; i++){
		c[a[i]] = true;
	}
	for (int i=0; i<m; i++){
		c[b[i]] = true;
	}

	ll v = 0;
	for (int i=1; i<40000; i++){
		if (!c[i]){
			v = i * i;
			break;
		}
	}

	ll k = v;
	while (true){
		bool mode = false;
		for (ll i: makediv(k)){
			ll j = k / i;
			bool ar = false;
			for (int x=0; x<n; x++){
				if (a[x]*a[x] <= i && i < (a[x]+1)*(a[x]+1)){
					ar = true;
				}
			}
			if (!ar) break;
			ar = false;
			for (int y=0; y<m; y++){
				if (b[y]*b[y] <= j && j < (b[y]+1)*(b[y]+1)){
					ar = true;
				}
			}
			if (ar){
				mode = true;
				break;
			}
		}
		if (!mode) break;
		k++;
	}
	cout << k << endl;
}