2016

using namespace std;

typedef long long ll;
typedef pair<ll, int> pii;
priority_queue<pii, vector<pii>, greater<pii> > q;
const int maxn = 1e5 + 5;
ll a[maxn], b[maxn];

int n, k;
ll sum;

pii (int j, int i){
    return pii(((b[i] + 1) * sum - (k + j) * a[i] + a[i] - 1) / a[i] + j, i);
}

int main(){
    ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
    cin >> n >> k;
    for(int i = 1; i <= n; i++) cin >> a[i], sum += a[i];
    for(int i = 1; i <= k; i++){
        int x;
        cin >> x;
        b[x]++;
    }
    for(int i = 1; i <= n; i++)q.emplace(cal(0, i));
    for(int i = 1; i <= sum + 1; i++){
        pii p = q.top();
        q.pop();
        b[p.second]++;
        q.emplace(cal(i, p.second));
        if(q.top().first <= i){
            cout << i - 1 << 'n';
            return 0;
        }
    }
    cout << "forevern";
    return 0;
}