#include <iostream>
#include <algorithm>
#define rep(i,n) for(ll i=0;i<(n);i++)

using namespace std;
using ll = long long;

//////////////////////////////////////////////////////////////////
ll N,A;
ll mod = 998244353;

ll solve(ll v,ll dist){
	if(v <= 0){
		return 0;
	}
	if(v == 1){
		return dist;
	}
	if(A == 1){
		if(v % 2 == 0){
			return ((v/2)%mod) * ((v-1)%mod)%mod;
		}else{
			return (v%mod) * (((v-1)/2)%mod)%mod;
		}
	}
	ll nv = ((v-1)/A)*A;
	ll ndist = dist  + 1;
	ll k = v - nv;
	ll sum;
	if(k % 2 == 0){
		sum = (((k/2)%mod)*((k-1)%mod))%mod + ((dist%mod) * (k%mod))%mod;
	}else{
		sum = ((k%mod)*(((k-1)/2)%mod))%mod + ((dist%mod) * (k%mod))%mod;
	}
	
	sum %= mod;
	
	ll sc = (sum + solve(nv,ndist))%mod;

	return sc;

}


int main(){
	ll T;ll ans = 0;
	cin >> T;
	rep(i,T){
		
		cin >> N >> A;

		ans = (solve(N,0))%mod;
		ans %= mod;

		cout << ans << endl;

	}
}