#include <bits/stdc++.h>
using namespace std;
long long int mod;
void prime(long long int a, vector<long long int>& v) {
  for (long long int i = 2ll; i * i <= a; i++) {
    if (a % i == 0ll) v.push_back(i);
    while (a % i == 0ll) {
      a = a / i;
    }
  }
  if (a > 1ll) v.push_back(a);
}
bool isprime(int a) {
  for (int i = 2; i * i <= a; i++)
    if (a % i == 0) return false;
  return true;
}
long long int expmod(long long int a, long long int b) {
  if (b == 1) return a;
  if (b == 0) return 1;
  long long int m1 = expmod(a, b / 2) % mod;
  if (b % 2) return ((m1 * m1) % mod * a % mod) % mod;
  return (m1 * m1) % mod;
}
long long int gcd(long long int a, long long int b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
long long int lcm(long long int a, long long int b) {
  return (a * b) / gcd(a, b);
}
struct myComp {
  constexpr bool operator()(pair<int, pair<int, int>> const& a,
                            pair<int, pair<int, int>> const& b) const noexcept {
    if (a.first < b.first) return true;
    if (a.first > b.first) return false;
    return a.second.first > b.second.first;
  }
};
int t, n, m, a[100005], b[100005];
bool vis[100005];
bool check(int num) {
  memset(vis, 0, sizeof(vis));
  int sum = 0, p = 0;
  for (int i = num; i >= 1; i--) {
    if (a[i] && !vis[a[i]]) {
      vis[a[i]] = 1;
      p += b[a[i]];
      sum++;
    } else {
      p--;
      if (p < 0) p = 0;
    }
  }
  return sum == m && !p;
}
int main() {
  t = 1;
  while (t--) {
    cin >> n >> m;
    for (int i = 1; i <= n; i++) cin >> a[i];
    for (int i = 1; i <= m; i++) cin >> b[i];
    int l = 1, r = n, ans = -1;
    while (l <= r) {
      int mid = (l + r) / 2;
      if (check(mid))
        r = mid - 1, ans = mid;
      else
        l = mid + 1;
    }
    printf("%d\n", ans);
  }
  return 0;
}
