#include <bits/stdc++.h>
using namespace std;
const int max_n = 5e5 + 10, max_f = 800;
struct Rad {
  int l, r;
  vector<pair<long long, int> > ar;
  long long s;
  Rad() {
    l = r = -1;
    s = 0;
  }
};
int n, q;
long long num[max_n];
Rad sq[max_n];
bool compare(const pair<long long, int> &a, const int &b) {
  return a.first < b;
}
bool compare2(const int &b, const pair<long long, int> &a) {
  return b < a.first;
}
void input() {
  scanf("%d%d", &n, &q);
  for (int i = 0; i < n; i++) scanf("%d", &num[i]);
  for (int i = 0; 1; i++) {
    sq[i].l = i * max_f;
    sq[i].r = min((i + 1) * max_f, n);
    for (int j = sq[i].l; j < sq[i].r; j++)
      sq[i].ar.push_back(make_pair(num[j], j));
    sort(sq[i].ar.begin(), sq[i].ar.end());
    if (sq[i].r == n) break;
  }
}
void modify(int l, int r, int x) {
  for (int i = 0; sq[i].l != -1; i++) {
    if (l <= sq[i].l && sq[i].r <= r) sq[i].s += x;
    if (sq[i].l < l && l < sq[i].r) {
      for (int j = l; j < min(sq[i].r, r); j++) num[j] += x;
      for (int j = sq[i].l; j < sq[i].r; j++)
        sq[i].ar[j - sq[i].l] = make_pair(num[j], j);
      sort(sq[i].ar.begin(), sq[i].ar.end());
    } else if (sq[i].l < r && r < sq[i].r) {
      for (int j = sq[i].l; j < r; j++) num[j] += x;
      for (int j = sq[i].l; j < sq[i].r; j++)
        sq[i].ar[j - sq[i].l] = make_pair(num[j], j);
      sort(sq[i].ar.begin(), sq[i].ar.end());
    }
  }
}
void output() {
  int type, l, r, x, y;
  int first, last, tmp, tmp2;
  for (int i = 0; i < q; i++) {
    scanf("%d", &type);
    if (type == 1) {
      scanf("%d%d%d", &l, &r, &x);
      modify(l - 1, r, x);
    } else {
      scanf("%d", &y);
      first = -1;
      for (int j = 0; sq[j].l != -1; j++) {
        tmp = lower_bound(sq[j].ar.begin(), sq[j].ar.end(), y - sq[j].s,
                          compare) -
              sq[j].ar.begin();
        tmp2 = upper_bound(sq[j].ar.begin(), sq[j].ar.end(), y - sq[j].s,
                           compare2) -
               sq[j].ar.begin() - 1;
        if (first == -1 && tmp != (int)sq[j].ar.size() &&
            sq[j].ar[tmp].first == y - sq[j].s)
          first = sq[j].ar[tmp].second;
        if (tmp2 != -1 && sq[j].ar[tmp2].first == y - sq[j].s)
          last = sq[j].ar[tmp2].second;
      }
      if (first == -1)
        printf("-1\n");
      else
        printf("%d\n", last - first);
    }
  }
}
int main() {
  input();
  output();
  return 0;
}
