#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;

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

		ans = 0;
		
		cin >> N >> A;

		ll v = N; ll dist = 0;

		if(A == 1){
			if(v % 2 == 0){
				ans = ((v/2)%mod) * ((v-1)%mod)%mod;
			}else{
				ans = (v%mod) * (((v-1)/2)%mod)%mod;
			}
		}else{
			while(true){

				if(v == 0){
					break;
				}
				if(v == 1){
					ans += dist;
					ans %= 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;

				ans += sum;
				ans %= mod;

				v = nv;dist = ndist;
			
			}
		}
		ans %= mod;
		std::cout << ans << endl;

	}
}