#include <bits/stdc++.h>
using namespace std;
const int maxn = 5e5 + 10;
const int bucket = 710;
long long a[maxn];
long long add[bucket];
set<long long> S[bucket];
int main(void) {
  int n, q;
  scanf("%d %d", &n, &q);
  for (int i = 0; i < n; i++) {
    scanf("%I64d", &a[i]);
    S[i / bucket].insert(a[i]);
  }
  for (int i = 0; i < q; i++) {
    int op;
    scanf("%d", &op);
    if (op == 1) {
      int l, r, x;
      scanf("%d %d %d", &l, &r, &x);
      --l, --r;
      int p = l / bucket, k = r / bucket;
      if (p == k) {
        S[p].clear();
        for (int i = p * bucket; i < min(n, (p + 1) * bucket); i++) {
          if (i >= l && i <= r) a[i] += 1ll * x;
          S[p].insert(a[i]);
        }
      } else {
        for (int i = p + 1; i < k; i++) add[i] += 1ll * x;
        S[p].clear();
        for (int i = p * bucket; i < min(n, (p + 1) * bucket); i++) {
          if (i >= l) a[i] += 1ll * x;
          S[p].insert(a[i]);
        }
        S[k].clear();
        for (int i = k * bucket; i < min(n, (k + 1) * bucket); i++) {
          if (i <= r) a[i] += 1ll * x;
          S[k].insert(a[i]);
        }
      }
    } else {
      int y;
      scanf("%d", &y);
      int l = -1, r = -1;
      for (int i = 0; i <= (n - 1) / bucket; i++) {
        if (l != -1) break;
        if (S[i].find(y - add[i]) != S[i].end()) {
          for (int j = i * bucket; j < min(n, (i + 1) * bucket); j++) {
            if (a[j] + add[i] == y) {
              l = j;
              break;
            }
          }
        }
      }
      for (int i = (n - 1) / bucket; i >= 0; i--) {
        if (r != -1) break;
        if (S[i].find(y - add[i]) != S[i].end()) {
          for (int j = min(n, (i + 1) * bucket) - 1; j >= i * bucket; j--) {
            if (a[j] + add[i] == y) {
              r = j;
              break;
            }
          }
        }
      }
      if (l != -1 && r != -1)
        printf("%d\n", r - l);
      else
        printf("-1\n");
    }
  }
}
