#include <bits/stdc++.h>   using namespace std;   const double one = 1.0;   const double PI = 3.14159265;   const long long maxn = 2e3 + 10;   const long long maxx = 1e6 + 10;   const long double eps = 1e-14;   const long long max_len = 1e6 + 1;   const long long mod1 = 1000000007;   const long long mod2 = 998244353;   long long dp[maxn][maxn];   void solve() {     long long n, k;     cin >> n >> k;     vector<long long> vl(n + 2);     for (long long i = 1; i < long long(n + 1); i++) cin >> vl[i];     for (long long i = 0; i < long long(n + 1); i++) {       for (long long j = 0; j < long long(n + 1); j++) dp[i][j] = 0;     }     for (long long i = 1; i < long long(n + 1); i++) {       for (long long j = 0; j < long long(i + 1); j++) {         dp[i][j] = max(dp[i][j], dp[i - 1][j] + (i - j == vl[i]));         if (j > 0) dp[i][j] = max(dp[i - 1][j - 1], dp[i][j]);       }     }     long long ans = 1000000000000000000;     for (long long j = 0; j < long long(n + 1); j++) {       if (dp[n][j] >= k) ans = min(ans, j);     }     if (ans >= 1000000000000000000) ans = -1;     cout << ans << endl;     return;   }   int main() {     ios_base::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     cerr.tie(0);     long long t;     cin >> t;     while (t--) solve();     return 0;   }   