#include <bits/stdc++.h>
using namespace std;
const int N = 500005, M = 1005;
using ll = long long;
int n, q, S;
ll tag[M];
vector<pair<ll, int>> v[M];
int main() {
  ios::sync_with_stdio(false);
  cin >> n >> q;
  S = sqrt(n) + 5;
  for (int i = 0; i < n; i++) {
    int tmp;
    cin >> tmp;
    v[i / S].push_back({tmp, i});
  }
  for (int i = 0; i <= (n - 1) / S; i++) sort(v[i].begin(), v[i].end());
  for (int _ = 1; _ <= q; _++) {
    int op, x;
    cin >> op;
    if (op == 1) {
      int l, r;
      cin >> l >> r >> x;
      --l;
      --r;
      int lb = l / S, rb = r / S;
      if (lb == rb) {
        for (auto &i : v[lb])
          if (i.second >= l && i.second <= r) i.first += x;
        sort(v[lb].begin(), v[lb].end());
      } else {
        for (auto &i : v[lb])
          if (i.second >= l) i.first += x;
        for (int i = lb + 1; i < rb; i++) tag[i] += x;
        for (auto &i : v[rb])
          if (i.second <= r) i.first += x;
        sort(v[lb].begin(), v[lb].end());
        sort(v[rb].begin(), v[rb].end());
      }
    } else {
      cin >> x;
      int lp = -1, rp = -1;
      for (int i = 0; i <= (n - 1) / S && lp == -1; i++) {
        auto it =
            lower_bound(v[i].begin(), v[i].end(), make_pair(x - tag[i], 0));
        if (it->first + tag[i] != x) continue;
        lp = it->second;
      }
      for (int i = (n - 1) / S; i >= 0 && rp == -1; --i) {
        auto it =
            lower_bound(v[i].begin(), v[i].end(), make_pair(x - tag[i] + 1, 0));
        if (it == v[i].begin() || ((--it)->first + tag[i] != x)) continue;
        rp = it->second;
      }
      if (lp == -1 || rp == -1) lp = 1, rp = 0;
      cout << rp - lp << endl;
    }
  }
  return 0;
}
