#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> PP;
// #define MOD 1000000007
#define MOD 998244353
#define INF 2305843009213693951
#define PI 3.141592653589
#define setdouble setprecision
#define REP(i,n) for(ll i=0;i<(n);++i)
#define OREP(i,n) for(ll i=1;i<=(n);++i)
#define RREP(i,n) for(ll i=(n)-1;i>=0;--i)
#define ORREP(i,n) for(ll i=(n);i>=1;--i)
#define rep(i,a,b) for(ll i=(a);i<=(b);++i)
#define ALL(v) (v).begin(), (v).end()
#define chmin(k,m) k = min(k,m)
#define chmax(k,m) k = max(k,m)
#define GOODBYE do { cout << "-1" << endl; return 0; } while (false)
#define MM <<" "<<
#define Endl endl

ll solve(ll N, ll A){

    if(A==1){
        ll Ans = (N*(N-1)/2)%MOD;
        return Ans;
    }

    ll M = N;
    ll Ans = 0;
    ll P = 1;
    while(N>0){

        ll nN = N/A;

        ll y = N%MOD;
        y = (y*P)%MOD;
        y = (M-y+MOD)%MOD;

        
        ll s = (N-nN)%MOD;
        Ans = (Ans+(y*s)%MOD)%MOD;

        ll w = s*(s-1)/2;
        w %= MOD;
        w = (w*P)%MOD;
        Ans = (Ans+w)%MOD;

        // cout << N MM nN MM y MM w << endl;

        N = nN;
        Ans += N;Ans%=MOD;
        P = (P*A)%MOD;

    }

    return Ans;

}

int main(void){
    //cin.tie(nullptr);
    //ios::sync_with_stdio(false);

    ll T;
    cin >> T;
    REP(_,T){
        ll N,A;
        cin >> N >> A;
        ll Ans = solve(N,A);
        cout << Ans << endl;
    }

    return 0;
    
}