#include <bits/stdc++.h>
using namespace std;
using ll = long long;

const ll MOD = 998244353;

ll modmul(ll a, ll b) {
    return (a % MOD) * (b % MOD) % MOD;
}

ll modadd(ll a, ll b) {
    return (a + b) % MOD;
}

ll dfs(ll n, ll a, map<ll, ll>& memo) {
    if (memo.count(n)) return memo[n];
    if (n == 1) return 0;

    ll res = 0;
    if (a == 1) {
        res = modmul(n % MOD, (n - 1) % MOD);
        res = modmul(res, (MOD + 1) / 2); 
        return memo[n] = res;
    }

    ll next = (n - 1) / a * a;
    ll count = n - next;
    
    ll add_sum = modmul(count % MOD, ((count - 1 + MOD) % MOD) * ((MOD + 1) / 2) % MOD);
    add_sum = modadd(add_sum, modmul(count % MOD, dfs(next, a, memo)));

    return memo[n] = add_sum % MOD;
}

int main() {
    int T;
    cin >> T;
    while (T--) {
        ll N, A;
        cin >> N >> A;
        map<ll, ll> memo;
        cout << dfs(N, A, memo) << endl;
    }
}