#include <bits/stdc++.h>
using namespace std;
const int MAXN = 5e5 + 69;
const int SQRT = 777;
int n, q;
long long arr[MAXN], lazy[SQRT];
unordered_map<long long, long long> key[SQRT];
int get_block(int indx) { return indx / SQRT; }
int get_highest_index(int val) {
  for (int i = get_block(n - 1); i >= 0; i--)
    if (key[i].count(val - lazy[i]))
      for (int it = min(n - 1, (i + 1) * SQRT - 1); it >= SQRT * i; it--)
        if (arr[it] == val - lazy[i]) return it;
  return -2;
}
int get_lowest_index(int val) {
  for (int i = 0; i <= get_block(n - 1); i++)
    if (key[i].count(val - lazy[i]))
      for (int it = SQRT * i; it <= min(n - 1, (i + 1) * SQRT - 1); it++)
        if (arr[it] == val - lazy[i]) return it;
  return -1;
}
void upd(int it, int val) {
  long long indx = get_block(it);
  key[indx][arr[it]] -= 1;
  if (!key[indx][arr[it]]) key[indx].erase(arr[it]);
  arr[it] += val;
  key[indx][arr[it]] += 1;
}
void update_block(int l, int r, int val) {
  long long it;
  for (int i = get_block(l) + 1; i < get_block(r); i++) lazy[i] += val;
  it = l;
  while (get_block(l) == get_block(it) and it <= r) upd(it, val), it++;
  it = r;
  if (get_block(l) != get_block(r))
    while (get_block(it) == get_block(r)) upd(it, val), it--;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long type, l, r, val;
  cin >> n >> q;
  for (int i = 0; i < n; i++) cin >> arr[i], key[get_block(i)][arr[i]] += 1;
  while (q--) {
    cin >> type;
    if (type == 1)
      cin >> l >> r >> val, update_block(l - 1, r - 1, val);
    else
      cin >> val,
          cout << get_highest_index(val) - get_lowest_index(val) << "\n";
  }
}
