#include <bits/stdc++.h>
using namespace std;
using u128 = unsigned __int128;

const long long M = 998244353;
long long m2 = (M + 1) / 2;

long long s(long long n, long long a) {
    long long nm = n % M;
    if (a == 1) {
        return nm * ((n - 1) % M) % M * m2 % M;
    }

    vector<long long> b = {1};
    while ((u128)b.back() * a <= n) {
        b.push_back(b.back() * a);
    }
    int L = (int)b.size() - 1;

    long long S = 0, T = 0, U = 1;
    for (int i = 0; i <= L; i++) {
        long long x = n / b[i];
        long long y = (i < L) ? n / b[i + 1] : 0;
        long long k = x - y;
        if (k > 0) {
            S = (S + (long long)i * (k % M)) % M;
            long long z = y + 1;
            long long w = ((z + x) % M * (k % M) % M * m2) % M;
            T = (T + (u128)w * U) % M;
        }
        U = (u128)U * a % M;
    }

    return (S + nm * nm % M - T + M) % M;
}

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

    int T;
    cin >> T;
    while (T--) {
        long long n, a;
        cin >> n >> a;
        cout << s(n, a) << "\n";
    }

    return 0;
}