#include <bits/stdc++.h>
using namespace std;
int n, q, l, r, x, y, rt, type, group[500100];
long long up[800], num[500100];
vector<pair<long long, int> > a[800];
int main() {
  scanf("%d%d", &n, &q);
  rt = int(ceil(sqrt(n)));
  int grp = 0;
  for (int i = 0; i < n; i++) {
    scanf("%d", &x);
    num[i] = x;
    a[grp].push_back(make_pair(x, i));
    group[i] = grp;
    if (a[grp].size() == rt) grp++;
  }
  for (int i = 0; i <= grp; i++) {
    sort(a[i].begin(), a[i].end());
  }
  while (q--) {
    scanf("%d", &type);
    if (type == 1) {
      scanf("%d%d%d", &l, &r, &x);
      l--, r--;
      for (int i = group[l] + 1; i <= group[r] - 1; i++) {
        up[i] += x;
      }
      a[group[l]].clear();
      a[group[r]].clear();
      for (int i = l, j = group[l]; group[i] == j and i <= r; i++) {
        num[i] += x;
      }
      int s = l, g = group[l];
      while (s >= 0 and group[s] == g) s--;
      s++;
      for (; s < n and group[s] == g; s++) {
        a[g].push_back(make_pair(num[s], s));
      }
      if (group[l] != group[r]) {
        for (int i = r, j = group[r]; group[i] == j; i--) {
          num[i] += x;
        }
        s = r, g = group[r];
        while (s >= 0 and group[s] == g) s--;
        s++;
        for (; s < n and group[s] == g; s++) {
          a[g].push_back(make_pair(num[s], s));
        }
      }
      sort(a[group[l]].begin(), a[group[l]].end());
      sort(a[group[r]].begin(), a[group[r]].end());
    } else {
      scanf("%d", &y);
      int mx = 0, mn = 10000000;
      for (int i = 0; i <= grp; i++) {
        if (a[i].size() == 0) continue;
        int lo = -1, hi = a[i].size() - 1, mid;
        while (lo + 1 < hi) {
          mid = (lo + hi) / 2;
          if (a[i][mid].first + up[i] >= y)
            hi = mid;
          else
            lo = mid;
        }
        if (a[i][hi].first + up[i] != y) continue;
        mn = min(mn, a[i][hi].second);
        lo = 0, hi = a[i].size();
        while (lo + 1 < hi) {
          mid = (lo + hi) / 2;
          if (a[i][mid].first + up[i] > y)
            hi = mid;
          else
            lo = mid;
        }
        if (a[i][lo].first + up[i] != y) continue;
        mx = max(mx, a[i][lo].second);
      }
      if (mn == 10000000) {
        printf("-1\n");
      } else {
        printf("%d\n", mx - mn);
      }
    }
  }
  return 0;
}
