#include <bits/stdc++.h>
#pragma GCC target("fma")
#pragma GCC optimize("unroll-loops,-Ofast")
using namespace std;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
long long a[500005];
int n;
set<long long> buck[1000];
long long c[1000];
void fix(int v) {
  int l = v * 700;
  int r = (v + 1) * 700;
  r = min(r, n);
  buck[v].clear();
  for (int i = l; i < r; ++i) {
    a[i] += c[v];
    buck[v].insert(a[i]);
  }
  c[v] = 0;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int q;
  cin >> n >> q;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
    buck[i / 700].insert(a[i]);
  }
  while (q--) {
    int t, l, r, x;
    cin >> t;
    if (t == 1) {
      cin >> l >> r >> x;
      --l;
      --r;
      if (l / 700 == r / 700) {
        for (int i = l; i <= r; i++) a[i] += x;
        fix(r / 700);
        continue;
      }
      if (l % 700 != 0) {
        for (; l % 700 != 0; ++l) {
          a[l] += x;
        }
        fix(l / 700 - 1);
      }
      l /= 700;
      if (r % 700 != 700 - 1) {
        for (; r % 700 != 700 - 1; --r) {
          a[r] += x;
        }
        fix(r / 700 + 1);
      }
      r /= 700;
      for (; l <= r; l++) c[l] += x;
    } else {
      cin >> x;
      l = r = -1;
      for (int i = 0; i <= n / 700; ++i) {
        if (buck[i].count(x - c[i])) {
          for (int j = i * 700; 1; ++j) {
            if (a[j] == x - c[i]) {
              l = j;
              break;
            }
          }
          break;
        }
      }
      for (int i = n / 700; i >= 0; --i) {
        if (buck[i].count(x - c[i])) {
          for (int j = i * 700 + 700 - 1; 1; --j) {
            if (a[j] == x - c[i]) {
              r = j;
              break;
            }
          }
          break;
        }
      }
      if (l == -1) {
        cout << -1 << '\n';
      } else {
        cout << r - l << '\n';
      }
    }
  }
}
