#include <bits/stdc++.h>
using namespace std;
using int64 = long long;
const int64 MOD = 998244353;
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int T;
    cin >> T;
    const int64 INV2 = (MOD + 1) / 2; // 2 の逆元
    while (T--)
    {
        int64 N, A;
        cin >> N >> A;
        if (A == 1)
        {
            // 全部 +1 だけ
            int64 n = N % MOD;
            int64 nm1 = (N - 1) % MOD;
            int64 ans = n * nm1 % MOD * INV2 % MOD;
            cout << ans << "\n";
            continue;
        }
        int64 ans = 0;
        int64 S = 0; // S_j を累積 (mod MOD)
        int64 x = N;
        while (x > 0)
        {
            int64 x_next = x / A;
            int64 L = x - x_next; // 区間長 L_j
            int64 Lm = L % MOD;
            // L_j * S_j
            int64 term1 = Lm * S % MOD;
            // L_j*(L_j-1)/2
            int64 term2 = Lm * ((L - 1) % MOD + MOD) % MOD * INV2 % MOD;
            ans = (ans + term1 + term2) % MOD;
            // 次の S_{j+1} = S_j + (r_j+1)
            int64 r = x % A;
            S = (S + (r % MOD) + 1) % MOD;
            x = x_next;
        }
        cout << ans << "\n";
    }
    return 0;
}