#include <bits/stdc++.h>
using namespace std;
int n, q;
int a[1000010];
int d[1000010];
int lowbit(int x) { return x & -x; }
void update(int x, int v) {
  while (x <= n) {
    d[x] += v;
    x += lowbit(x);
  }
}
int query(int x) {
  int res = 0;
  while (x) {
    res += d[x];
    x -= lowbit(x);
  }
  return res;
}
int main() {
  scanf("%d%d", &n, &q);
  for (int i = 1; i <= n; i++) {
    scanf("%d", &a[i]);
    update(a[i], 1);
  }
  while (q--) {
    int k;
    scanf("%d", &k);
    if (k > 0)
      update(k, 1);
    else {
      k = -k;
      int l = 1, r = n, pos = -1;
      while (l <= r) {
        int mid = (l + r) >> 1;
        if (query(mid) < k) {
          l = mid + 1;
        } else {
          r = mid - 1;
          pos = mid;
        }
      }
      if (pos != -1) update(pos, -1);
    }
  }
  int ans = -1;
  for (int i = 1; i <= n; i++) {
    if (query(i) - query(i - 1)) {
      ans = i;
      break;
    }
  }
  printf("%d", (ans == -1 ? 0 : ans));
  return 0;
}
