#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include<bits/stdc++.h>
#include<atcoder/all>
using namespace std;
using namespace atcoder; 
using ll=long long;
using mint=modint998244353;
const ll inf=(1e9+7)*(1e9+7);
int dx[4]={1,0,0,-1},dy[4]={0,1,-1,0};
const int mod=998244353;
using P=pair<ll,int>;
int main(){
	int t;
	ll n,a;
	cin>>t;
	while(cin>>n>>a){
		if(a==1){
			mint m=n;
			cout<<(m*(m-1)/2).val()<<endl;
		}else{
			vector<ll>v={n};
			while(v.back()!=0)
				v.push_back(v.back()/a);
			mint ans=0,tmp=0;
			for(int i=0;i+1<v.size();i++){
				ans+=(v[i]+tmp)*(v[i]-v[i+1])-(v[i]+v[i+1]+mint(1))*(v[i]-v[i+1])/2;
				tmp+=1+v[i]%a;
			}
			cout<<ans.val()<<endl;
		}
	}
}