#include <bits/stdc++.h>
using namespace std;
//#include<atcoder/all>
//using namespace atcoder;
using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
constexpr ll MAX = 2000000000000000000;
constexpr ld PI = 3.14159265358979;
constexpr ll MOD = 998244353;//2024948111;
ld dotorad(ld K){ return PI * K / 180.0; }
ld radtodo(ld K){ return K * 180.0 / PI; }
mt19937 mt;
void randinit(){ srand((unsigned)time(NULL));mt = mt19937(rand()); }
void solve(){
    ll N,A;
    cin >> N >> A;
    if(A == 1){
        ll a = (1 + N - 1) % MOD;
        ll b = (N - 1) % MOD;
        if(a % 2 == 0) a /= 2;
        else b /= 2;
        ll ans = a * b;
        ans %= MOD;
        cout << ans << endl;
        return;
    }
    ll s = 1,last = N,ans = 0;
    for(ll p = 0;p <= 100;p++){
        if(last == 1) break;
        ll sa;
        if(MAX / A < s) sa = MAX;
        else sa = s * A;
        ll st = (N / (sa)) + 1;
        //cerr << st << " " << last << endl;
        if(last == st) break;
        ll m = 0,cp = N;
        for(ll i = 0;i < p;i++){
            m += cp % A;
            cp /= A;
        }
        ll lst = (last - st);
        lst %= MOD;
        ans += (lst * (p % MOD)) % MOD;
        ans += (lst * (m % MOD)) % MOD;
        ans %= MOD;
        ll hiku = N / s;
        ans += (lst * (hiku % MOD)) % MOD;
        ans %= MOD;
        {
            ll a = (last - st);
            ll b = (last + st - 1);
            if(a % 2 == 0) a /= 2;
            else b /= 2;
            a %= MOD;
            b %= MOD;
            ans -= (a * b) % MOD;
        }
        ans %= MOD;
        if(ans < 0) ans += MOD;
        // cerr << "ans = " << ans << endl;
        last = st;
        if(MAX / A < s) break;
        s *= A;
    }
    cout << ans << endl;
}
int main(){
    ll T;
    cin >> T;
    while(T--){
        solve();
    }
}