include<bits/stdc++.h>

using namespace std;

define ll long long

define endl "\n"

int main() { int t; cin>>t; while(t--){ ll n,k; cin>>n>>k; vector b; b.assign(k,0); for(ll i=0;i<n;i++){ ll a; cin>>a; if((a%k)!=0) b[k-(a%k)]++; } ll maxi=1,index=0; for(ll i=1;i<k;i++){ if(maxi<=b[i]){ maxi=b[i]; index=i; } } for(ll i=0;i<maxi-1;i++){ index+=k; } if(index==0) cout<<index<<endl; else cout<<index+1<<endl;

}
return 0;

} Can anybody explain it to me? plz

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