#include <bits/stdc++.h>
using namespace std;
const long long maxn = 5e5 + 10;
long long a[maxn];
long long be[maxn];
long long bk[maxn];
vector<pair<long long, long long> > vs[maxn];
long long kkk;
long long n;
void update(long long l, long long r, long long x) {
  if (be[l] == be[r]) {
    long long id = be[l];
    if (bk[id]) {
      for (long long i = id * kkk - kkk + 1; i <= min(id * kkk, n); i++)
        a[i] += bk[id];
      bk[id] = 0;
    }
    for (long long i = l; i <= r; i++) {
      a[i] += x;
    }
    vs[id].clear();
    for (long long i = id * kkk - kkk + 1; i <= min(id * kkk, n); i++) {
      vs[id].push_back({a[i], i});
    }
    sort(vs[id].begin(), vs[id].end());
    return;
  }
  long long id = be[l];
  if (bk[id]) {
    for (long long i = id * kkk - kkk + 1; i <= min(id * kkk, n); i++)
      a[i] += bk[id];
    bk[id] = 0;
  }
  for (long long i = l; i <= min(id * kkk, n); i++) a[i] += x;
  vs[id].clear();
  for (long long i = id * kkk - kkk + 1; i <= min(id * kkk, n); i++)
    vs[id].push_back({a[i], i});
  sort(vs[id].begin(), vs[id].end());
  id = be[r];
  if (bk[id]) {
    for (long long i = id * kkk - kkk + 1; i <= min(id * kkk, n); i++)
      a[i] += bk[id];
    bk[id] = 0;
  }
  for (long long i = id * kkk - kkk + 1; i <= r; i++) a[i] += x;
  vs[id].clear();
  for (long long i = id * kkk - kkk + 1; i <= min(id * kkk, n); i++)
    vs[id].push_back({a[i], i});
  sort(vs[id].begin(), vs[id].end());
  for (long long i = be[l] + 1; i <= be[r] - 1; i++) bk[i] += x;
}
long long query(long long y) {
  long long p = 1e18;
  long long q = 0;
  for (long long i = 1; i <= be[n]; i++) {
    long long id = lower_bound(vs[i].begin(), vs[i].end(),
                               pair<long long, long long>({y - bk[i], 0})) -
                   vs[i].begin();
    if (vs[i][id].first == y - bk[i]) {
      p = min(p, vs[i][id].second);
      q = max(q, vs[i][id].second);
    }
    id = upper_bound(vs[i].begin(), vs[i].end(),
                     pair<long long, long long>({y - bk[i], 1000005})) -
         vs[i].begin();
    if (id - 1 < 0) continue;
    if (vs[i][id - 1].first == y - bk[i]) {
      p = min(p, vs[i][id - 1].second);
      q = max(q, vs[i][id - 1].second);
    }
  }
  if (p > q)
    return -1;
  else
    return q - p;
}
int32_t main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long q;
  cin >> n >> q;
  for (long long i = 1; i <= n; i++) cin >> a[i];
  kkk = sqrt(n);
  for (long long i = 1; i <= n; i++) {
    be[i] = (i - 1) / kkk + 1;
    vs[be[i]].push_back({a[i], i});
  }
  for (long long i = 1; i <= be[n]; i++) {
    sort(vs[i].begin(), vs[i].end());
  }
  while (q--) {
    long long x;
    cin >> x;
    if (x == 1) {
      long long l, r, k;
      cin >> l >> r >> k;
      update(l, r, k);
    }
    if (x == 2) {
      long long y;
      cin >> y;
      cout << query(y) << endl;
    }
  }
}
