#include <bits/stdc++.h>
using namespace std;
const int N = 500010, G = 1010;
int n, q, koren;
long long a[N], d[N];
pair<long long, int> pa[G][G];
int grupa(int x) { return 1 + (x - 1) / koren; }
void sortirajgrupu(int grp, int neki) {
  int vel = 0;
  for (int i = neki; i && grupa(i) == grp; i--) pa[grp][++vel] = {a[i], i};
  for (int i = neki + 1; i <= n && grupa(i) == grp; i++)
    pa[grp][++vel] = {a[i], i};
  sort(pa[grp] + 1, pa[grp] + vel + 1);
}
int main() {
  scanf("%d %d", &n, &q);
  koren = sqrt(n);
  for (int i = 1; i <= n; i++) scanf("%I64d", &a[i]);
  for (int i = 1, g = 1; g <= n; i++, g += koren) sortirajgrupu(i, g);
  while (q--) {
    int t;
    scanf("%d", &t);
    if (t == 1) {
      int l, r, x;
      scanf("%d %d %d", &l, &r, &x);
      int p = grupa(l), q = grupa(r);
      if (p == q) {
        for (int i = l; i <= r; i++) a[i] += x;
        sortirajgrupu(p, l);
        continue;
      }
      for (int i = l; i <= n && grupa(i) == p; i++) a[i] += x;
      for (int i = r; i && grupa(i) == q; i--) a[i] += x;
      sortirajgrupu(p, l);
      sortirajgrupu(q, r);
      for (int i = p + 1; i < q; i++) d[i] += x;
    } else {
      int x, mi = 0, ma;
      scanf("%d", &x);
      for (int i = 1, g = 1; g <= n; i++, g += koren) {
        int gor = min(n, g + koren - 1), vel = gor - g + 1;
        int pos = lower_bound(pa[i] + 1, pa[i] + vel + 1,
                              pair<long long, int>(x - d[i], 1)) -
                  pa[i];
        if (pos <= vel && pa[i][pos].first == x - d[i]) {
          mi = pa[i][pos].second;
          break;
        }
      }
      for (int i = (n + koren - 1) / koren, g = (i - 1) * koren + 1; i;
           i--, g -= koren) {
        int gor = min(n, g + koren - 1), vel = gor - g + 1;
        int pos = lower_bound(pa[i] + 1, pa[i] + vel + 1,
                              pair<long long, int>(x - d[i] + 1, 1)) -
                  pa[i] - 1;
        if (pos && pa[i][pos].first == x - d[i]) {
          ma = pa[i][pos].second;
          break;
        }
      }
      if (mi)
        printf("%d\n", ma - mi);
      else
        printf("-1\n");
    }
  }
  return 0;
}
