#include <bits/stdc++.h>
using namespace std;
long long MOD;
long long a[1234567];
long long toAdd[1234567];
int index(int x, int size) {
  if (x % size == 0) return x / size - 1;
  return x / size;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int n, q;
  cin >> n >> q;
  int size = min(400, n);
  int count = n / size;
  if (n % size != 0) count++;
  for (int i = 1; i <= n; ++i) cin >> a[i];
  vector<unordered_map<long long, int> > mapki;
  for (int i = 0; i < count; ++i) {
    for (int j = 1; j <= size; ++j) {
      int index = i * size + j;
      mapki.push_back(unordered_map<long long, int>());
      mapki[i][a[index]]++;
    }
  }
  for (int qq = 0; qq < q; ++qq) {
    int query;
    cin >> query;
    if (query == 1) {
      int l, r;
      long long x;
      cin >> l >> r >> x;
      int li = index(l, size);
      int ri = index(r, size);
      for (int i = li + 1; i <= ri - 1; ++i) toAdd[i] += x;
      if (li < ri) {
        for (int i = l; i <= (li + 1) * size; ++i) {
          if (mapki[li][a[i]] > 1)
            mapki[li][a[i]]--;
          else
            mapki[li].erase(a[i]);
          mapki[li][a[i] + x]++;
          a[i] += x;
        }
        for (int i = ri * size + 1; i <= r; ++i) {
          if (mapki[ri][a[i]] > 1)
            mapki[ri][a[i]]--;
          else
            mapki[ri].erase(a[i]);
          mapki[ri][a[i] + x]++;
          a[i] += x;
        }
      } else {
        for (int i = l; i <= r; ++i) {
          if (mapki[ri][a[i]] > 1)
            mapki[ri][a[i]]--;
          else
            mapki[ri].erase(a[i]);
          mapki[ri][a[i] + x]++;
          a[i] += x;
        }
      }
    } else {
      long long y;
      cin >> y;
      int left = 0;
      int right = 0;
      bool found = false;
      for (int i = 0; i < count; ++i) {
        if (mapki[i].find(y - toAdd[i]) != mapki[i].end()) {
          found = true;
          for (int j = 1 + i * size; j <= (i + 1) * size; ++j) {
            if (a[j] == y - toAdd[i]) {
              left = j;
              break;
            }
          }
          break;
        }
      }
      if (!found) {
        cout << "-1\n";
        continue;
      }
      for (int i = count - 1; i >= 0; --i) {
        if (mapki[i].find(y - toAdd[i]) != mapki[i].end()) {
          for (int j = (i + 1) * size; j >= 1 + i * size; --j) {
            if (a[j] == y - toAdd[i]) {
              right = j;
              break;
            }
          }
          break;
        }
      }
      cout << (right - left) << "\n";
    }
  }
}
