#include <bits/stdc++.h>
using namespace std;
int const inf = 2000000009;
int const maxn = 550006;
int const LQ = 750;
map<unsigned int, int> lft[LQ * 2];
map<unsigned int, int> rht[LQ * 2];
unsigned int a[maxn];
unsigned int add[LQ * 2];
inline void recalc(int i) {
  lft[i].clear();
  rht[i].clear();
  int l = i * LQ;
  int r = l + LQ - 1;
  for (int j = l; j <= r; ++j) rht[i][a[j]] = j;
  for (int j = r; j >= l; --j) lft[i][a[j]] = j;
}
int main() {
  ios_base::sync_with_stdio(false);
  int n, q;
  cin >> n >> q;
  for (int i = 0; i < n; ++i) cin >> a[i];
  int NQ = 1 + n / LQ;
  for (int i = 0; i < NQ; ++i) recalc(i);
  stringstream OUT;
  for (int i = 0; i < q; ++i) {
    int type = 0;
    cin >> type;
    if (type == 1) {
      int l, r, x;
      cin >> l >> r >> x;
      --l;
      --r;
      int leftq = l + (LQ - l % LQ);
      int rightq = r - r % LQ;
      int start = leftq / LQ;
      int finish = rightq / LQ;
      if (leftq < rightq) {
        for (int j = start; j < finish; ++j) {
          add[j] += x;
          if (add[j] > inf) add[j] = inf;
        };
        if (l < leftq) {
          for (int j = l; j < leftq; ++j) {
            a[j] += x;
            if (a[j] > inf) a[j] = inf;
          };
          recalc(start - 1);
        }
        if (r >= rightq) {
          for (int j = rightq; j <= r; ++j) {
            a[j] += x;
            if (a[j] > inf) a[j] = inf;
          };
          recalc(finish);
        }
      } else {
        for (int j = l; j <= r; ++j) {
          a[j] += x;
          if (a[j] > inf) a[j] = inf;
        };
        recalc(start - 1);
        recalc(finish);
      }
    } else {
      int x;
      cin >> x;
      int left_find = maxn;
      int right_find = -maxn;
      for (int j = 0; j < NQ; ++j) {
        if (x >= add[j]) {
          auto it = lft[j].find(x - add[j]);
          if (it != lft[j].end()) {
            left_find = it->second;
            break;
          }
        }
      }
      if (left_find < maxn) {
        for (int j = NQ - 1; j >= 0; --j) {
          if (x >= add[j]) {
            auto it = rht[j].find(x - add[j]);
            if (it != rht[j].end()) {
              right_find = it->second;
              break;
            }
          }
        }
      }
      OUT << (left_find > right_find ? -1 : right_find - left_find) << '\n';
    }
  }
  cout << OUT.str();
  return 0;
}
