653D.cpp

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*/                              
#include<bits/stdc++.h>
using namespace std;
 
#define fastio ios_base::sync_with_stdio(0); cin.tie(0)
#define LL long long 
#define mod 1000000007 
#define FOR(i, j, k) for (int i=j ; i<k ; i++)
#define ROF(i, j, k) for (int i=j ; i>=k ; i--) 
#define debug(...) fprintf(stderr, __VA_ARGS__), fflush(stderr)
#define time__(d) for(long blockTime = 0; (blockTime == 0 ? (blockTime=clock()) != 0 : false); debug("%s time : %.4fs", d, (double)(clock() - blockTime) / CLOCKS_PER_SEC))

const long long INF = 1e18;
const long long MAX = 1e5+10;
int main(){
    fastio;
    int t=1; cin>>t;
    while(t--){
        LL n,k,x;  cin>>n>>k;map<LL,LL>m;
        int  cnt=0;
        FOR(i,0,n){ 
            cin>>x;
            if(x%k==0) {cnt++ ; continue;}
            m[k - x%k]++;
        } if(cnt==n) {cout<<0<<"\n"; continue;}
        LL ans = 0,mx=0,j=0;
        for(auto i : m){
            if(mx<=i.second) mx=i.second,j=i.first;
        }    
        cout<<(mx-1)*k + j+1<<"\n";
    }
}