#include <bits/stdc++.h>
using namespace std;
vector<pair<long long, int> > x[710];
long long of[710];
inline void rm(int id) {
  if (of[id]) {
    vector<pair<long long, int> > &v = x[id];
    for (int i = 0; i < v.size(); ++i) v[i].first += of[id];
    of[id] = 0;
  }
}
int main() {
  int n, q;
  scanf("%d%d", &n, &q);
  int z = sqrt(n);
  int k = 0, j = 0;
  for (int i = 0; i < n; ++i) {
    if (k == z) k = 0, ++j;
    int t;
    scanf("%d", &t);
    x[j].push_back(make_pair(t, i));
    ++k;
  }
  ++j;
  for (int i = 0; i < j; ++i) sort(x[i].begin(), x[i].end());
  while (q--) {
    int o;
    scanf("%d", &o);
    if (o == 1) {
      int l, r, t;
      scanf("%d%d%d", &l, &r, &t);
      --l, --r;
      int p = l / z, q = r / z;
      rm(p), rm(q);
      vector<pair<long long, int> > &v = x[p];
      if (p == q) {
        for (int i = 0; i < v.size(); ++i)
          if (v[i].second >= l && v[i].second <= r) v[i].first += t;
        sort(v.begin(), v.end());
      } else {
        for (int i = 0; i < v.size(); ++i)
          if (v[i].second >= l) v[i].first += t;
        sort(v.begin(), v.end());
        vector<pair<long long, int> > &v = x[q];
        for (int i = 0; i < v.size(); ++i)
          if (v[i].second <= r) v[i].first += t;
        sort(v.begin(), v.end());
        for (int i = p + 1; i < q; ++i) of[i] += t;
      }
    } else {
      int t;
      scanf("%d", &t);
      int l = -1, r = -1, i = 0;
      while (i < j) {
        vector<pair<long long, int> >::iterator it =
            lower_bound(x[i].begin(), x[i].end(), make_pair(t - of[i], 0));
        if (it != x[i].end() && it->first == t - of[i]) {
          l = it->second;
          break;
        }
        ++i;
      }
      i = j - 1;
      while (i >= 0) {
        vector<pair<long long, int> >::iterator it = upper_bound(
            x[i].begin(), x[i].end(), make_pair(t - of[i], (int)1e7));
        if (it != x[i].begin() && (--it)->first == t - of[i]) {
          r = it->second;
          break;
        }
        --i;
      }
      if (l == -1)
        printf("-1\n");
      else
        printf("%d\n", r - l);
    }
  }
}
