#include <bits/stdc++.h>
using namespace std;
set<pair<long long int, int> > st[800];
set<pair<long long int, int> >::iterator it;
long long int add[800], A[500005];
int main() {
  int n, q;
  scanf("%d %d", &n, &q);
  for (int i = 0; i < n; i++) {
    int a;
    scanf("%d", &a);
    st[i / 700].insert(pair<long long int, int>(a, i));
    A[i] = a;
  }
  int sz = (n - 1) / 700;
  for (int i = 0; i < q; i++) {
    int t;
    scanf("%d", &t);
    if (t == 1) {
      int l, r, x;
      scanf("%d %d %d", &l, &r, &x);
      l--;
      r--;
      int L = l / 700, R = r / 700;
      if (L == R) {
        while (l <= r) {
          st[L].erase(pair<long long int, int>(A[l], l));
          A[l] += x;
          st[L].insert(pair<long long int, int>(A[l], l));
          l++;
        }
      } else {
        bool ok = l % 700 == 0;
        while (l % 700 != 0) {
          st[L].erase(pair<long long int, int>(A[l], l));
          A[l] += x;
          st[L].insert(pair<long long int, int>(A[l], l));
          l++;
        }
        if (!ok) L++;
        ok = (r + 1) % 700 == 0;
        while ((r + 1) % 700 != 0) {
          st[R].erase(pair<long long int, int>(A[r], r));
          A[r] += x;
          st[R].insert(pair<long long int, int>(A[r], r));
          r--;
        }
        if (!ok) R--;
        while (L <= R) add[L++] += x;
      }
    } else {
      long long int y;
      scanf("%I64d", &y);
      int left = -1, right = -1;
      for (int j = 0; j <= sz; j++) {
        it = st[j].lower_bound(pair<long long int, int>(y - add[j], -1));
        if (it != st[j].end()) {
          pair<long long int, int> p = *it;
          if (p.first == y - add[j]) {
            left = p.second;
            break;
          }
        }
      }
      if (left == -1)
        puts("-1");
      else {
        for (int j = sz; j >= 0; j--) {
          it = st[j].upper_bound(pair<long long int, int>(y - add[j] + 1, -1));
          if (it != st[j].begin())
            ;
          {
            it--;
            pair<long long int, int> p = *it;
            if (p.first == y - add[j]) {
              right = p.second;
              break;
            }
          }
        }
        printf("%d\n", right - left);
      }
    }
  }
  return 0;
}
