/**
	author:  shobonvip
	created: 2025.04.20 01:26:58
**/

#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;
}

const mint inv2 = mint(2).inv();

void solve() {
	ll n, a;
	cin >> n >> a;

	if (a == 1) {
		mint ans = mint(n) * mint(n-1) * inv2;
		cout << ans.val() << '\n';
		return;
	}

	vector<ll> koho;
	vector<ll> costs;
	ll x = n;
	ll c = 0;
	while (x > 0) {
		koho.push_back(x);
		costs.push_back(c);
		c += x % a;
		c += 1;
		x /= a;
	}

	koho.push_back(0);
	mint ans = 0;
	rep(i,0,(int)koho.size()-1) {
		ll v = koho[i] - koho[i+1];
		ans += mint(v) * mint(v-1) * inv2;
		ans += mint(v) * costs[i];
	}

	cout << ans.val() << endl;
}

int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	
	int t; cin >> t;
	while (t--) {
		solve();
	}
}