#include <bits/stdc++.h>
using namespace std;
int n, query, boxsize, boxcnt;
long long A[500005], boxoffset[5000];
map<pair<long long, int>, int> M[5000];
void update(int L, int R, int x) {
  int Lbox = L / boxsize;
  int Rbox = R / boxsize;
  for (int i = Lbox + 1; i <= Rbox - 1; i++) {
    boxoffset[i] += x;
  }
  int st = L - (Lbox * boxsize);
  for (int i = Lbox * boxsize + st; i < min(R + 1, (Lbox + 1) * boxsize); i++) {
    M[Lbox].erase(make_pair(A[i], i));
    A[i] += x;
    M[Lbox][make_pair(A[i], i)] = 1;
  }
  if (Lbox != Rbox) {
    st = R - (Rbox * boxsize);
    for (int i = (Rbox)*boxsize + st; i >= max(L, (Rbox)*boxsize); i--) {
      M[Rbox].erase(make_pair(A[i], i));
      A[i] += x;
      M[Rbox][make_pair(A[i], i)] = 1;
    }
  }
}
int answer(int val) {
  int Lidx = -1, Ridx = -1;
  for (int i = 0; i <= boxcnt; i++) {
    if (M[i].empty()) continue;
    auto it = M[i].lower_bound(make_pair((long long)val - boxoffset[i], -1));
    if (it != M[i].end() && it->first.first == (long long)val - boxoffset[i]) {
      Lidx = it->first.second;
      break;
    }
  }
  if (Lidx == -1) return -1;
  for (int i = boxcnt; i >= 0; i--) {
    if (M[i].empty()) continue;
    auto it = M[i].lower_bound(
        make_pair((long long)val - boxoffset[i] + (long long)1, -1));
    if (it == M[i].begin()) continue;
    --it;
    if (it->first.first == (long long)val - boxoffset[i]) {
      Ridx = it->first.second;
      break;
    }
  }
  return Ridx - Lidx;
}
int main() {
  scanf("%d %d", &n, &query);
  boxsize = sqrt(n);
  boxcnt = n / boxsize;
  if (boxsize * boxcnt != n) {
    ++boxcnt;
  }
  for (int i = 0; i < n; i++) {
    scanf("%I64d", &A[i]);
    int boxnum = i / boxsize;
    M[boxnum][make_pair(A[i], i)] = 1;
  }
  for (int l, r, x, y, flag, i = 1; i <= query; i++) {
    scanf("%d", &flag);
    if (flag == 1) {
      scanf("%d %d %d", &l, &r, &x);
      --l;
      --r;
      update(l, r, x);
    } else {
      scanf("%d", &y);
      int ans = answer(y);
      printf("%d\n", ans);
    }
  }
}
