#include <bits/stdc++.h>
using namespace std;
vector<vector<long long> > vec(500005);
vector<long long>::iterator it;
long long a[500005], ty[500005];
long long block = 750;
int main() {
  std::ios::sync_with_stdio(false);
  long long n, q, i, j, val2, val, val1, l, r, x, y;
  cin >> n >> q;
  for (i = 0; i < n; i++) {
    cin >> a[i];
  }
  for (i = 0; i < n; i++) {
    vec[i / block].push_back(a[i]);
  }
  val2 = (n - 1) / block;
  val2 += 10;
  for (i = 0; i < val2 + 1; i++) {
    sort(vec[i].begin(), vec[i].end());
  }
  for (j = 0; j < q; j++) {
    cin >> x;
    long long minn = (1000 * 1000 * 1000 + 5), lo = (1000 * 1000 * 1000 + 5),
              hi = -1;
    long long maxx = -1;
    if (x == 1) {
      cin >> l >> r >> x;
      l--;
      r--;
      val = l / block;
      val1 = r / block;
      if (val == val1) {
        for (i = l; i < r + 1; i++) {
          a[i] += x;
        }
        vec[val].clear();
        for (i = val * block; i < min(n, (val + 1) * block); i++) {
          vec[val].push_back(a[i]);
        }
        sort(vec[val].begin(), vec[val].end());
      } else {
        vec[val].clear();
        vec[val1].clear();
        for (i = l; i < (val + 1) * block; i++) {
          a[i] += x;
        }
        for (i = val * block; i < min(n, (val + 1) * block); i++) {
          vec[val].push_back(a[i]);
        }
        sort(vec[val].begin(), vec[val].end());
        for (i = (val1)*block; i < r + 1; i++) {
          a[i] += x;
        }
        for (i = val1 * block; i < min(n, (val1 + 1) * block); i++) {
          vec[val1].push_back(a[i]);
        }
        sort(vec[val1].begin(), vec[val1].end());
        for (i = val + 1; i < val1; i++) {
          ty[i] += x;
        }
      }
    } else {
      cin >> y;
      for (i = 0; i < val2 + 1; i++) {
        it = lower_bound(vec[i].begin(), vec[i].end(), y - ty[i]);
        if (it != vec[i].end()) {
          if (*it == y - ty[i]) {
            lo = min(lo, i);
            hi = max(hi, i);
          }
        }
      }
      if (hi != -1) {
        for (i = lo * block; i < min(n, (lo + 1) * block); i++) {
          if (a[i] + ty[lo] == y) {
            minn = i;
            break;
          }
        }
        for (i = hi * block; i < min(n, (hi + 1) * block); i++) {
          if (a[i] + ty[hi] == y) {
            maxx = max(maxx, i);
          }
        }
      }
      if (maxx != -1) {
        cout << maxx - minn << endl;
      } else {
        cout << -1 << endl;
      }
    }
  }
}
