#include <bits/stdc++.h> using namespace std; typedef long long ll; template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return true; } return false; } template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return true; } return false; } #define vi vector<int> #define vl vector<ll> #define vii vector<pair<int,int>> #define vll vector<pair<ll,ll>> #define vvi vector<vector<int>> #define vvl vector<vector<ll>> #define vvii vector<vector<pair<int,int>>> #define vvll vector<vector<pair<ll,ll>>> #define vst vector<string> #define pii pair<int,int> #define pll pair<ll,ll> #define pb push_back #define all(x) (x).begin(),(x).end() #define mkunique(x) sort(all(x));(x).erase(unique(all(x)),(x).end()) #define fi first #define se second #define mp make_pair #define si(x) int(x.size()) const int mod=998244353,MAX=300005; const ll INF=15LL<<58; int main(){ std::ifstream in("text.txt"); std::cin.rdbuf(in.rdbuf()); cin.tie(0); ios::sync_with_stdio(false); int Q;cin>>Q; while(Q--){ ll N,K;cin>>N>>K; vl X(N); ll sum=0; for(int i=0;i<N;i++){ cin>>X[i]; sum+=X[i]%K; } if(sum%K){ cout<<-1<<"\n"; continue; } sort(all(X),[&](ll a,ll b){ if(a%K==b%K) return a<b; else return a%K<b%K; }); ll T=sum/K; vl Y(N); ll ma=0; for(int i=0;i<N;i++){ Y[i]=X[i]%K; chmax(ma,Y[i]); } if(ma<=T){ cout<<T<<"\n"; continue; } ll ans=INF; for(int q=0;q<3*N;q++){ for(int i=0;i<N;i++){ if(Y[i]<X[i]){ Y[i]+=K; T++; chmax(ma,Y[i]); if(ma<=T) chmin(ans,T); } } } if(ans==INF) ans=-1; cout<<ans<<"\n"; } }