#include <bits/stdc++.h>
using namespace std;
int a[1000002], b[4000000], intialsum[1000003];
int q(int ind) {
  int sum = 0;
  while (ind > 0) {
    sum += b[ind];
    ind -= ind & (-ind);
  }
  return sum;
}
void u(int ind, int n, int val) {
  while (ind <= n) {
    b[ind] += val;
    ind += ind & (-ind);
  }
}
int main() {
  {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
  };
  int i, j, k, l, n, m, t, h;
  cin >> n >> k;
  for (i = 1; i <= n; i++) {
    cin >> j;
    a[j]++;
  }
  for (i = 1; i <= n; i++) intialsum[i] = intialsum[i - 1] + a[i];
  for (i = 1; i <= k; i++) {
    cin >> j;
    if (j > 0) {
      a[j]++;
      u(j, n, 1);
    } else {
      l = 1;
      h = n;
      while (h > l) {
        m = (l + h) >> 1;
        if (intialsum[m] + q(m) >= -j)
          h = m;
        else
          l = m + 1;
      }
      a[l]--;
      u(l, n, -1);
    }
  }
  for (i = 1; i <= n; i++)
    if (a[i] > 0) return cout << i << endl, 0;
  cout << 0 << endl;
  return 0;
}
