#include <bits/stdc++.h> #include <bits/stdc++.h> #include <bits/stdc++.h> using namespace std; // #include <atcoder/modint> // using namespace atcoder; // using mint = modint998244353; using ll = long long; #define fix(x) fixed << setprecision(x) #define rep(i, n) for(int i = 0; i < n; ++i) #define all(x) (x).begin(),(x).end() template<class T>bool chmin(T&a, const T&b){if(a>b){a=b;return 1;}return 0;} template<class T>bool chmax(T&a, const T&b){if(a<b){a=b;return 1;}return 0;} constexpr ll INFLL = (1LL << 62), MOD = 998244353; constexpr int INF = (1 << 30); int main(){ cin.tie(nullptr); ios::sync_with_stdio(false); int t; cin >> t; while(t--){ int n,k; cin >> n >> k; vector<ll> a[2]; int tot = 0; rep(i,n){ ll x; cin >> x; a[x>=k].emplace_back(x%k); tot += x%k; } if(tot%k){ cout << "-1\n"; continue; } if(!tot){ cout << "0\n"; continue; } int l = -1, r = a[1].size()+1, ans = -1; sort(all(a[1])); reverse(all(a[1])); while(l+1<r){ int md = (l+r)/2, cnt = 0; priority_queue<int> pq; for(int x:a[0]) pq.emplace(x); rep(i,a[1].size()) pq.emplace(a[1][i]+k*(i<md)); bool f = true; while(f && pq.top()>0){ ++cnt; vector<int> v; rep(i,k){ if(!pq.top()){ f = false; break; } v.emplace_back(pq.top()-1); pq.pop(); } for(int x:v) pq.emplace(x); } if(f) r = md, ans = cnt; else l = md; } cout << ans << '\n'; } return 0; }