#include <bits/stdc++.h>
using namespace std;
#define ls u << 1
#define rs u << 1 | 1
#define LL long long
#define int long long
#define PII pair <int, int>
#define fi first
#define se second
#define pub push_back
#define pob pop_back
#define puf push_front
#define pof pop_front
#define lb lower_bound
#define ub upper_bound
#define i128 __int128
#define pcnt(x) __builtin_popcount(x)
#define mem(a,goal) memset(a, (goal), sizeof(a))
#define rep(x,start,end) for(int x = (start) - ((start) > (end)); x != (end) - ((start) > (end)); ((start) < (end) ? x ++ : x --))
#define aLL(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
const int INF = 998244353;
const int mod = 1e9 + 7;
const int N = 100010;
int st[N], primes[N];
int cnt;
void get()
{
    for(int i = 2; i < 40001; ++ i)
    {
        if(!st[i]) primes[cnt ++] = i;
        for(int j = 0; i * primes[j] < 40001; ++ j)
        {
            st[i * primes[j]] = 1;
            if(i % primes[j] == 0) break;
        }
    }
}
void solve()
{
    get();//2262
    int n, m, res = 0;
    cin >> n >> m;
    vector<int> a(n, 0), b(m, 0);
    for(int i = 0; i < n; ++ i) cin >> a[i];
    for(int i = 0; i < m; ++ i) cin >> b[i];
    sort(a.begin(), a.end());
    sort(b.begin(), b.end());
    for(int i = 0; i < cnt; ++ i)
    {
        int t = primes[i];
        if(t > n + m) break;
        int l = 0, r = m - 1;
        while(l < n && r >= 0)
        {
            if(a[l] + b[r] > t)
            {
                -- r;
                continue;
            }
            if(a[l] + b[r] < t)
            {
                ++ l;
                continue;
            }
            if(a[l] + b[r] == t)
            {
                ++ res;
                break;
            }
        }
    }
    cout << res << '\n';
}

signed main()
{
    int t = 1;
    while (t --) solve();
    return 0;
}