#include <bits/stdc++.h>
using namespace std;
const long long MAXN = 1e6;
const long long inf = 1e9;
vector<vector<pair<long long, long long> > > b;
long long n, m, a[MAXN], d[MAXN];
int main() {
  cin >> n >> m;
  for (long long i = 0; i < n; ++i) cin >> a[i];
  b.resize(n);
  long long len = sqrt(n) + 1;
  for (long long i = 0; i < n; ++i) b[i / len].push_back(make_pair(a[i], i));
  long long cnt = (n - 1) / len + 1;
  for (long long i = 0; i < cnt; ++i) sort(b[i].begin(), b[i].end());
  while (m--) {
    long long c;
    cin >> c;
    if (c == 1) {
      long long l, r, x;
      cin >> l >> r >> x;
      l--;
      r--;
      for (long long i = l; i <= r;) {
        if (i % len == 0 && i + len - 1 <= r)
          d[i / len] += x, i += len;
        else
          a[i] += x, i++;
      }
      long long s = l / len;
      for (long long i = s * len; i < min(s * len + len, n); ++i)
        b[s][i % len] = make_pair(a[i], i);
      sort(b[s].begin(), b[s].end());
      s = r / len;
      for (long long i = s * len; i < min(s * len + len, n); ++i)
        b[s][i % len] = make_pair(a[i], i);
      sort(b[s].begin(), b[s].end());
    } else {
      long long x;
      cin >> x;
      long long l = -1, r = -1;
      for (long long i = 0; i < cnt && l == -1; ++i) {
        vector<pair<long long, long long> >::iterator c =
            lower_bound(b[i].begin(), b[i].end(),
                        pair<long long, long long>(x - d[i], -inf));
        if (c->first == x - d[i] && c->second < n && c->second >= 0)
          l = c->second;
      }
      for (long long i = cnt - 1; i >= 0 && r == -1; --i) {
        vector<pair<long long, long long> >::iterator c =
            --lower_bound(b[i].begin(), b[i].end(),
                          pair<long long, long long>(x - d[i] + 1, -inf));
        if (c->first == x - d[i] && c->second < n && c->second >= 0)
          r = c->second;
      }
      if (l == -1 || r - l < 0)
        cout << -1 << endl;
      else
        cout << r - l << endl;
    }
  }
  return 0;
}
