#include <bits/stdc++.h>
#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math,O3")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
using namespace std;
const long long N = 5e5 + 10;
const long long M = 3e8 + 1;
const long long big = 1e18;
const long long shift = 1000;
const long long hsh2 = 1964325029;
const long long mod = 998244353;
const long double EPS = 1e-14;
const long long block = 800;
mt19937 srnd(chrono::steady_clock::now().time_since_epoch().count());
long long n, q;
long long a[N];
vector<pair<long long, long long> > z[N];
long long second[N];
void upd1(long long b, long long L, long long R, long long x) {
  long long l = max(1ll, b * block);
  long long r = min(n, (b + 1) * block - 1);
  for (int i = max(l, L); i <= min(R, r); i++) a[i] += x;
  z[b].clear();
  for (int i = l; i <= r; i++) z[b].push_back(make_pair(a[i], i));
  sort((z[b]).begin(), (z[b]).end());
}
void upd(long long l, long long r, long long x) {
  int lb = l / block, rb = r / block;
  upd1(lb, l, r, x);
  if (lb != rb) upd1(rb, l, r, x);
  for (int j = lb + 1; j < rb; j++) second[j] += x;
}
long long L = big, R = 0, l;
void check(long long j, long long u) {
  if (u >= 0 && u < z[j].size() && z[j][u].first == l - second[j])
    L = min(z[j][u].second, L), R = max(z[j][u].second, R);
}
int main() {
  ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  cin >> n >> q;
  long long cnt = n / block + 1;
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
    z[i / block].push_back(make_pair(a[i], i));
  }
  for (int i = 0; i < cnt; i++) sort((z[i]).begin(), (z[i]).end());
  while (q--) {
    long long t, r, x;
    cin >> t >> l;
    if (t == 1)
      cin >> r >> x, upd(l, r, x);
    else {
      L = big;
      R = 0;
      for (int j = 0; j < cnt; j++) {
        check(j, lower_bound((z[j]).begin(), (z[j]).end(),
                             make_pair(l - second[j], 0ll)) -
                     z[j].begin());
        check(j, upper_bound((z[j]).begin(), (z[j]).end(),
                             make_pair(l - second[j] + 1, 0ll)) -
                     z[j].begin() - 1);
      }
      cout << max(-1ll, R - L) << '\n';
    }
  }
}
