#include <bits/stdc++.h>
using namespace std;
const int maxn = 5 * 1e5 + 50;
int q, n;
long long a[maxn], ch[maxn];
vector<vector<pair<long long, int> > > v;
int main() {
  ios_base::sync_with_stdio(0);
  cin >> n >> q;
  int len = ceil(sqrt(n));
  int cnt = ceil(n / (double)len);
  v.resize(n);
  for (int i = 0; i < n; i++) cin >> a[i];
  for (int i = 0; i < n; i++) v[i / len].push_back(make_pair(a[i], i));
  for (int i = 0; i < cnt; i++) sort(v[i].begin(), v[i].end());
  int type, l, r, x, mn, mx, idx;
  while (q--) {
    cin >> type;
    if (type == 1) {
      cin >> l >> r >> x;
      l--;
      r--;
      for (int i = l; i <= r;) {
        if (i % len == 0 && i + len <= r) {
          ch[i / len] += x;
          i += len;
        } else {
          a[i] += x;
          i++;
        }
      }
      idx = l / len;
      v[idx].clear();
      for (int i = idx * len; i < n && i / len == idx; i++)
        v[idx].push_back(make_pair(a[i], i));
      sort(v[idx].begin(), v[idx].end());
      idx = r / len;
      v[idx].clear();
      for (int i = idx * len; i < n && i / len == idx; i++)
        v[idx].push_back(make_pair(a[i], i));
      sort(v[idx].begin(), v[idx].end());
    } else {
      cin >> x;
      mn = 2e9, mx = 0;
      for (int i = 0; i < cnt; i++) {
        idx = lower_bound(v[i].begin(), v[i].end(), make_pair(x - ch[i], 0)) -
              v[i].begin();
        if (idx < v[i].size() && v[i][idx].first == x - ch[i])
          mn = min(mn, v[i][idx].second);
        idx =
            lower_bound(v[i].begin(), v[i].end(), make_pair(x - ch[i] + 1, 0)) -
            v[i].begin();
        idx--;
        if (idx < v[i].size() && v[i][idx].first == x - ch[i])
          mx = max(mx, v[i][idx].second);
      }
      if (mx - mn < 0)
        cout << -1 << '\n';
      else
        cout << mx - mn << '\n';
    }
  }
}
