#include <bits/stdc++.h>
using namespace std;
long long a[500005], inc[1002], n, q, d;
vector<pair<long long, long long> > v[1002];
int main() {
  ios::sync_with_stdio(false);
  cin.tie(), cout.tie();
  cin >> n >> q;
  d = sqrt(n);
  long long cnt = 1;
  for (int i = 1; i <= n; i++) {
    long long x;
    cin >> x;
    v[cnt].push_back({x, i});
    if (i % d == 0) {
      sort(v[cnt].begin(), v[cnt].end());
      cnt++;
    }
  }
  sort(v[cnt].begin(), v[cnt].end());
  while (q--) {
    long long t, l, r, x;
    cin >> t;
    if (t == 1) {
      cin >> l >> r >> x;
      long long lower = ceil(l / (double)d);
      long long upper = ceil(r / (double)d);
      for (int i = 0; i < v[lower].size(); i++) {
        if (v[lower][i].second >= l && v[lower][i].second <= r)
          v[lower][i].first += x;
      }
      sort(v[lower].begin(), v[lower].end());
      if (upper != lower) {
        for (int i = 0; i < v[upper].size(); i++) {
          if (v[upper][i].second >= l && v[upper][i].second <= r)
            v[upper][i].first += x;
        }
        sort(v[upper].begin(), v[upper].end());
      }
      for (int i = lower + 1; i < upper; i++) inc[i] += x;
    } else {
      cin >> x;
      long long l = 1e18, r = -1e18;
      for (int i = 1; i <= cnt; i++) {
        x -= inc[i];
        if (v[i].size() == 0) continue;
        long long lo = 0, hi = v[i].size() - 1;
        while (lo <= hi) {
          long long mid = (lo + hi) / 2;
          if (v[i][mid].first == x) {
            l = min(l, v[i][mid].second);
            hi = mid - 1;
          } else if (v[i][mid].first > x)
            hi = mid - 1;
          else
            lo = mid + 1;
        }
        lo = 0, hi = v[i].size() - 1;
        while (lo <= hi) {
          long long mid = (lo + hi) / 2;
          if (v[i][mid].first == x) {
            r = max(r, v[i][mid].second);
            lo = mid + 1;
          } else if (v[i][mid].first > x)
            hi = mid - 1;
          else
            lo = mid + 1;
        }
        x += inc[i];
      }
      if (l == 1e18)
        cout << -1 << endl;
      else
        cout << r - l << endl;
    }
  }
}
