#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

int main()
{
    ll n, m;
    cin >> n >> m;
    bitset<200010> dp;
    for (int i = 0; i < n; ++i) {
        ll u;
        cin >> u;
        dp[u] = 1;
    }
    for (int i = 0; i < m; ++i) {
        ll t;
        cin >> t;
        dp |= dp << t;
    }
    cout << dp.count() << endl;
}