description: In Berland, n different types of banknotes are used. Banknotes of the i-th type have denomination 10^{a_i} burles (burles are the currency used in Berland); the denomination of banknotes of the first type is exactly 1.
  
  Let's denote f(s) as the minimum number of banknotes required to represent exactly s burles. For example, if the denominations of banknotes used in Berland are 1, 10 and 100, then f(59) = 14: 9 banknotes with denomination of 1 burle and 5 banknotes with denomination of 10 burles can be used to represent exactly 9 ⋅ 1 + 5 ⋅ 10 = 59 burles, and there's no way to do it with fewer banknotes.
  
  For a given integer k, find the minimum positive number of burles s that cannot be represented with k or fewer banknotes (that is, f(s) > k).
  
  Input
  
  The first line contains a single integer t (1 ≤ t ≤ 10^4) — number of test cases.
  
  The first line of each test case contains two integers n and k (1 ≤ n ≤ 10; 1 ≤ k ≤ 10^9).
  
  The next line contains n integers a_1, a_2, ..., a_n (0 = a_1 < a_2 < ... < a_n ≤ 9).
  
  Output
  
  For each test case, print one integer — the minimum positive number of burles s that cannot be represented with k or fewer banknotes.
  
  Example
  
  Input
  
  
  4
  3 13
  0 1 2
  2 777
  0 4
  3 255
  0 1 3
  10 1000000000
  0 1 2 3 4 5 6 7 8 9
  
  
  Output
  
  
  59
  778
  148999
  999999920999999999
solution: #include <bits/stdc++.h>
  using namespace std;
  long long tc = 1;
  int main() {
    ios::sync_with_stdio(0);
    long long ten[20];
    ten[0] = 1;
    string nine[20];
    for (int i = 1; i <= 18; i++) {
      ten[i] = ten[i - 1] * 10;
      nine[i] = nine[i - 1] + '9';
    }
    long long t;
    cin >> t;
    while (t--) {
      long long n, k;
      cin >> n >> k;
      long long a[n + 5], seg[n + 5], baki = 19;
      for (int i = 0; i < n; i++) cin >> a[i];
      if (n == 1) {
        cout << k + 1 << "\n";
        continue;
      }
      for (int i = n - 1; i >= 0; i--) {
        seg[i] = baki - a[i];
        baki = a[i];
      }
      string s;
      for (int i = 0; i < n; i++) {
        if (ten[seg[i]] - 1 > k || k == 0) {
          cout << k + 1 << s << "\n";
          break;
        }
        s += nine[seg[i]];
        k -= (ten[seg[i]] - 1);
      }
    }
    return 0;
  }
  