#include <bits/stdc++.h>
using namespace std;

long long mod = 998244353;
//入力が必ず-mod<a<modの時.
struct mint{
    long long v = 0;
    mint(){} mint(int a){v = a<0?a+mod:a;} mint(long long a){v = a<0?a+mod:a;}
    mint(unsigned long long a){v = a;}
    long long val(){return v;}
    void modu(){v %= mod;}
 
    mint repeat2mint(const long long a,long long b){
        mint ret = 1,p = a;
        while(b){
            if(b&1) ret *= p;
            p *= p; b >>= 1;
        }
        return ret;
    };
 
    mint &operator=(const mint &b) = default;
    mint operator-() const {return mint(0)-(*this);}
    mint operator+(const mint b){return mint(v)+=b;}
    mint operator-(const mint b){return mint(v)-=b;}
    mint operator*(const mint b){return mint(v)*=b;}
    mint operator/(const mint b){return mint(v)/=b;}
 
    mint operator+=(const mint b){
        v += b.v; if(v >= mod) v -= mod;
        return *this;
    }
    mint operator-=(const mint b){
        v -= b.v; if(v < 0) v += mod; 
        return *this;
    }   
    mint operator*=(const mint b){v = v*b.v%mod; return *this;}
    mint operator/=(mint b){
        if(b == 0) assert(false);
        int left = mod-2;
        while(left){if(left&1) *this *= b; b *= b; left >>= 1;}
        return *this;
    }
 
    mint operator++(int){*this += 1; return *this;}
    mint operator--(int){*this -= 1; return *this;}
    bool operator==(const mint b){return v == b.v;}
    bool operator!=(const mint b){return v != b.v;}
    bool operator>(const mint b){return v > b.v;}
    bool operator>=(const mint b){return v >= b.v;}
    bool operator<(const mint b){return v < b.v;}
    bool operator<=(const mint b){return v <= b.v;}
 
    mint pow(const long long x){return repeat2mint(v,x);}
    mint inv(){return mint(1)/v;}
};

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int T; cin >> T;
    while(T--){
        long long N,K; cin >> N >> K;
        vector<long long> A;
        long long ok = 0,sum = 0;
        while(N--){
            long long a; cin >> a;
            if(a == 0) continue;
            a %= K; sum += a;
            if(a) A.push_back(a);
            else ok++;
        }
        N = A.size();
        if(N == 0){cout << "0\n"; continue;}
        if(sum%K){cout << "-1\n"; continue;}

        long long answer = 1e18;
        for(int t=0; t<=min(K-1,ok); t++){
            vector<long long> C(K+1);
            for(auto &a : A) C.at(a)++;
            C.at(K) = t;
            priority_queue<long long,vector<long long>,greater<>> Q;
            long long zero = 0;
            for(int i=K; i>=0; i--) while(C.at(i)--){
                long long now = zero+i;
                Q.push(now);
                if(Q.size() == K){
                    long long left = Q.top()-zero;
                    zero += left;
                    while(Q.size() && Q.top() == zero) Q.pop(); 
                }
            }
            if(Q.size()) continue;
            answer = min(answer,zero);
        }
        if(answer > 9e17) answer = -1;
        cout << answer << "\n";
    }
}