#include <bits/stdc++.h>
const long long maxn = 1e6;
const long long maxsq = 1000;
long long val[maxn];
std::unordered_map<long long, long long> m[maxsq];
long long inc[maxsq];
long long sq;
int main() {
  long long n, q;
  std::cin >> n >> q;
  sq = std::min(n, (long long)std::ceil(std::sqrt(n)));
  for (long long i = 0; i < n; i++) {
    std::cin >> val[i];
    m[i / sq][val[i]]++;
  }
  for (long long i = 0; i < q; i++) {
    long long type;
    std::cin >> type;
    if (type == 1) {
      long long l, r, x;
      std::cin >> l >> r >> x;
      l--, r--;
      long long l_block = l / sq;
      long long r_block = r / sq;
      for (long long j = l_block + 1; j <= r_block - 1; j++) {
        inc[j] += x;
      }
      for (long long j = l; j / sq == l_block and j <= r; j++) {
        auto ite = m[l_block].find(val[j]);
        if (ite != m[l_block].end()) {
          ite->second--;
          if (ite->second == 0) {
            m[l_block].erase(ite);
          }
        }
        val[j] += x;
        m[l_block][val[j]]++;
      }
      if (l_block != r_block) {
        for (long long j = r; j / sq == r_block; j--) {
          auto ite = m[r_block].find(val[j]);
          if (ite != m[r_block].end()) {
            ite->second--;
            if (ite->second == 0) {
              m[r_block].erase(ite);
            }
          }
          val[j] += x;
          m[r_block][val[j]]++;
        }
      }
    } else {
      long long value;
      std::cin >> value;
      long long least = n + 1, most = -1;
      for (long long j = 0; j < sq; j++) {
        auto ite = m[j].find(value - inc[j]);
        if (ite != m[j].end()) {
          least = std::min(least, j);
          most = std::max(most, j);
        }
      }
      if (least == n + 1) {
        std::cout << -1 << '\n';
      } else {
        long long least_seen = -1;
        long long most_seen = -1;
        for (long long j = least * sq; j < (least + 1) * sq; j++) {
          if (val[j] + inc[least] == value) {
            least_seen = j;
            break;
          }
        }
        for (long long j = most * sq; j < (most + 1) * sq; j++) {
          if (val[j] + inc[most] == value) {
            most_seen = j;
          }
        }
        std::cout << most_seen - least_seen << '\n';
      }
    }
  }
}
