#include <bits/stdc++.h>
#include <atcoder/modint>
using namespace std;
using ll = long long;
using mint = atcoder::modint998244353;
#define fast cin.tie(nullptr); ios_base::sync_with_stdio(false)

ll digsum(ll n, ll a) {
    ll res = 0;
    while(n){
        res += n % a;
        n /= a;
    }
    return res;
}

mint sum(ll n, ll a) {
    if(a == 1) {
        return mint(n) * mint(n - 1) / 2;
    }
    ll k = 0, power = 1;
    mint ans = 0;
    while(power <= n) {
        mint f = mint(n / power) + mint(digsum(n % power, a)) + mint(k);
        mint factor = mint(n / power - n / (power * a));
        ans += f * factor;
        if(power > n / a) break;
        power *= a;
        k++;
    }
    mint dec = mint(n) * mint(n + 1) / 2;
    return ans - dec;
}

int main() {
    fast;
    ll t, n, a;
    cin >> t;
    while(t--){
        cin >> n >> a;
        cout << sum(n, a).val() << "\n";
    }
    return 0;
}