#include <bits/stdc++.h>
int main() {
  using namespace std;
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int n, q;
  cin >> n >> q;
  vector<int> bit(n + 1, 0);
  auto upd = [&](int pos, int val) -> void {
    while (pos <= n) {
      bit[pos] += val;
      pos += (pos & -pos);
    }
  };
  auto sum = [&](int a) -> int {
    int res = 0;
    while (a) {
      res += bit[a];
      a -= (a & -a);
    }
    return res;
  };
  auto query = [&](int a, int b) -> int { return sum(b) - sum(a - 1); };
  for (int i = 0; i < n; i++) {
    int a;
    cin >> a;
    upd(a, 1);
  }
  for (int i = 0; i < q; i++) {
    int X;
    cin >> X;
    if (X < 0) {
      X = -X;
      int low = 0, high = n + 1;
      while (low < high) {
        int mid = (low + high) >> 1;
        if (sum(mid) >= X) {
          high = mid;
        } else {
          low = mid + 1;
        }
      }
      upd(low, -1);
    } else {
      upd(X, 1);
    }
  }
  for (int i = 1; i <= n; i++) {
    if (sum(i) > sum(i - 1)) {
      cout << i << "\n";
      return 0;
    }
  }
  cout << "0\n";
}
