#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 4000000000000000001

int get(int n){
	int r = sqrt(n);
	if(r*r <= n && n < (r+1)*(r+1))return r;
	if(r*r>n)r++;
	else r--;
	return r;
}

int main(){
	
	int n,m;
	cin>>n>>m;
	vector<int> a(n),b(m);
	rep(i,n)cin>>a[i];
	rep(i,m)cin>>b[i];
	
	for(int i=1;true;i++){
		if(a[0]==1&&binary_search(b.begin(),b.end(),i))continue;
		if(b[0]==1&&binary_search(a.begin(),a.end(),i))continue;
		
		for(int j=i*i;true;j++){
			bool f = false;
			for(int k=1;k*k<=j;k++){
				if(j%k==0){
					int x = k;
					int y = j/k;
					rep(_,2){
						if(binary_search(a.begin(),a.end(),get(x))&&binary_search(b.begin(),b.end(),get(y))){
							f = true;
							goto L;
						}
						
						swap(x,y);
					}
				}
				
			}
			L:;
			if(!f){
				cout<<j<<endl;
				return 0;
			}
		}
		
	}
	
	return 0;
}