#include <bits/stdc++.h>
using namespace std;
const long long N = 5e5 + 10, SQ = 750, M = N / SQ + 50;
long long n, q, too_add[M];
vector<pair<long long, long long> > v[M];
void build() {
  for (long long i = 0; i < n; i += SQ) {
    long long g = i / SQ;
    sort(v[g].begin(), v[g].end());
  }
}
void add(long long l, long long r, long long x) {
  long long gl = l / SQ, gr = r / SQ;
  for (long long i = gl + 1; i < gr; i++) too_add[i] += x;
  if (gl == gr) {
    for (long long i = 0; i < v[gl].size(); i++)
      if (v[gl][i].second >= l && v[gl][i].second <= r) v[gl][i].first += x;
    sort(v[gl].begin(), v[gl].end());
    return;
  }
  for (long long i = 0; i < v[gl].size(); i++)
    if (v[gl][i].second >= l && v[gl][i].second <= r) v[gl][i].first += x;
  for (long long i = 0; i < v[gr].size(); i++)
    if (v[gr][i].second <= r && v[gr][i].second >= l) v[gr][i].first += x;
  sort(v[gl].begin(), v[gl].end());
  sort(v[gr].begin(), v[gr].end());
}
long long GukiZiana(long long k) {
  long long l = -1, r = -2;
  for (long long i = 0; i < n; i += SQ) {
    long long g = i / SQ;
    long long lindx =
        lower_bound(v[g].begin(), v[g].end(),
                    pair<long long, long long>(k - too_add[g], 0)) -
        v[g].begin();
    long long rindx =
        lower_bound(v[g].begin(), v[g].end(),
                    pair<long long, long long>(k - too_add[g], n + 1)) -
        v[g].begin() - 1;
    if (rindx < 0 || lindx >= v[g].size() ||
        v[g][lindx].first != k - too_add[g])
      continue;
    if (l == -1) l = v[g][lindx].second;
    r = v[g][rindx].second;
  }
  return r - l;
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cin >> n >> q;
  for (long long i = 0; i < n; i++) {
    long long x;
    cin >> x;
    v[i / SQ].push_back({x, i});
  }
  build();
  for (long long t = 0; t < q; t++) {
    long long type, l, r, x;
    cin >> type;
    if (type == 1) {
      cin >> l >> r >> x;
      l--;
      r--;
      add(l, r, x);
    } else {
      cin >> x;
      cout << GukiZiana(x) << '\n';
    }
  }
}
