#include <bits/stdc++.h>
using namespace std;
const long long inf = 1e9;
const long long inf_ll = 1e18;
const long long N = 500005, S = 800;
long long a[S][S], c[S];
multiset<long long> f[S];
void inc(long long i, long long x) {
  long long& y = a[i / S][i % S];
  f[i / S].erase(f[i / S].find(y));
  y += x;
  f[i / S].insert(y);
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long n, q;
  cin >> n >> q;
  for (long long i = 0; i < n; i++) {
    cin >> a[i / S][i % S];
    f[i / S].insert(a[i / S][i % S]);
  }
  while (q--) {
    long long t;
    cin >> t;
    if (t == 1) {
      long long l, r, x;
      cin >> l >> r >> x;
      l--, r--;
      if (l / S == r / S)
        for (long long i = l; i <= r; i++) inc(i, x);
      else {
        for (long long i = l / S + 1; i < r / S; i++) c[i] += x;
        for (long long i = l; i < (l / S + 1) * S; i++) inc(i, x);
        for (long long i = (r / S) * S; i <= r; i++) inc(i, x);
      }
    } else {
      long long y;
      cin >> y;
      long long l = inf, r = -inf;
      ;
      for (long long i = 0; i <= (n - 1) / S; i++)
        if (f[i].find(y - c[i]) != f[i].end())
          l = min(l, i * S), r = max(r, (i + 1) * S - 1);
      if (l == inf)
        cout << "-1\n";
      else {
        while (a[l / S][l % S] != y - c[l / S]) l++;
        while (a[r / S][r % S] != y - c[r / S]) r--;
        cout << r - l << "\n";
      }
    }
  }
}
