#include <bits/stdc++.h>
using namespace std;
const int maxn = 500010;
int n;
long long int v[maxn], lazy[maxn];
pair<long long int, int> t[maxn];
int SQRT;
int N;
void recalc(int idx) {
  int a = idx * SQRT, b = min(n, (idx + 1) * SQRT);
  for (int i = a; i < b; i++) {
    v[i] += lazy[idx];
    t[i] = make_pair(v[i], i);
  }
  lazy[idx] = 0;
  sort(t + a, t + b);
}
void add(int a, int b, long long int delta) {
  int idx_a = a / SQRT, idx_b = b / SQRT;
  if (idx_a == idx_b) {
    for (int i = a; i <= b; i++) v[i] += delta;
    recalc(idx_a);
  } else {
    for (int i = a, lim = min(n, (idx_a + 1) * SQRT); i < lim; i++)
      v[i] += delta;
    recalc(idx_a);
    for (int i = idx_a + 1; i < idx_b; i++) lazy[i] += delta;
    for (int i = idx_b * SQRT; i <= b; i++) v[i] += delta;
    recalc(idx_b);
  }
}
int query(long long int val) {
  int x = INT_MAX, y = INT_MIN;
  for (int idx = 0; idx < N; idx++) {
    int a = idx * SQRT, b = min(n, (idx + 1) * SQRT);
    long long int nval = val - lazy[idx];
    int pos = lower_bound(t + a, t + b, make_pair(nval, -1)) - t;
    if (pos != b && t[pos].first == nval) x = min(x, t[pos].second);
    pos = lower_bound(t + a, t + b, make_pair(nval + 1, -1)) - t - 1;
    if (pos != (a - 1) && t[pos].first == nval) y = max(y, t[pos].second);
  }
  if (x == INT_MAX) return -1;
  return y - x;
}
int main() {
  int q;
  scanf("%d %d", &n, &q);
  for (int i = 0; i < n; i++) {
    scanf("%lld", v + i);
  }
  SQRT = (int)sqrt(n) + 1;
  N = (n + SQRT - 1) / SQRT;
  for (int idx = 0; idx < N; idx++) {
    recalc(idx);
  }
  while (q--) {
    int type;
    scanf("%d", &type);
    if (type == 1) {
      int l, r;
      long long int x;
      scanf("%d %d %lld", &l, &r, &x);
      add(l - 1, r - 1, x);
    } else {
      long long int x;
      scanf("%lld", &x);
      printf("%d\n", query(x));
    }
  }
  return 0;
}
