/** author: shobonvip created: 2025.03.07 22:05:11 **/ #pragma GCC optimize("Ofast") #pragma GCC optimize("unroll-loops") #include<bits/stdc++.h> using namespace std; //* ATCODER #include<atcoder/all> using namespace atcoder; typedef modint998244353 mint; //*/ /* BOOST MULTIPRECISION #include<boost/multiprecision/cpp_int.hpp> using namespace boost::multiprecision; //*/ typedef long long ll; #define rep(i, s, n) for (int i = (int)(s); i < (int)(n); i++) #define rrep(i, s, n) for (int i = (int)(n)-1; i >= (int)(s); i--) #define all(v) v.begin(), v.end() template <typename T> bool chmin(T &a, const T &b) { if (a <= b) return false; a = b; return true; } template <typename T> bool chmax(T &a, const T &b) { if (a >= b) return false; a = b; return true; } template <typename T> T max(vector<T> &a){ assert(!a.empty()); T ret = a[0]; for (int i=0; i<(int)a.size(); i++) chmax(ret, a[i]); return ret; } template <typename T> T min(vector<T> &a){ assert(!a.empty()); T ret = a[0]; for (int i=0; i<(int)a.size(); i++) chmin(ret, a[i]); return ret; } template <typename T> T sum(vector<T> &a){ T ret = 0; for (int i=0; i<(int)a.size(); i++) ret += a[i]; return ret; } ll op(ll a,ll b) { return a + b; } ll e(){ return 0; } void solve() { ll k, n; cin >> n >> k; vector<ll> a(n); vector<ll> b(n); vector<ll> c(n); ll s = 0; rep(i,0,n) { cin >> a[i]; b[i] = a[i] - a[i] / k * k; c[i] = a[i] / k; s += b[i]; } vector<ll> d = c; sort(all(d)); if (s % k != 0) { cout << -1 << '\n'; return; } if (s == 0) { cout << 0 << '\n'; return; } auto check = [&](ll i) -> ll { ll p = i + s/k; ll freedom = 0; ll cost = 0; vector<ll> amari(k); rep(i,0,n) { if (b[i] > p) { cost += p; }else { freedom += min(c[i], (p - b[i]) / k); if (a[i] > p) { amari[(p - b[i]) % k] += 1; } cost += b[i]; } } ll left = i; { ll targ = min(freedom, left); freedom -= targ; left -= targ; cost += targ * k; } rrep(i,0,k) { ll targ = min(amari[i], left); left -= targ; amari[i] -= targ; cost += targ * i; } return p*k-cost; }; ll ub=sum(c); ll lb=0; while(ub-lb>2){ ll t1=(ub*2+lb)/3; ll t2=(ub+lb*2)/3; if(check(t1)<=check(t2)){ lb=t2; }else{ ub=t1; } } bool mode=0; ll ind=-1; for(ll i=lb;i<=ub;i++){ if(check(i)<=0){ mode=1; ind=i; break; } } if(!mode){ cout<<-1<<'\n'; return; } ll lb2=-1; ll ub2=ind; while(ub2-lb2>1){ ll t=(ub2+lb2)/2; if(check(t)<=0)ub2=t; else lb2=t; } cout<<ub2+s/k<<endl; } int main(){ ios_base::sync_with_stdio(false); cin.tie(NULL); int t; cin >> t; while(t--) solve(); }