#include<atcoder/all>
using namespace atcoder;

#include <bits/stdc++.h>
template<class T> inline bool chmin(T&a, T b){if(a > b){a = b; return true;}else{return false;}}
template<class T> inline bool chmax(T&a, T b){if(a < b){a = b; return true;}else{return false;}}
#define ll long long
#define double long double
#define rep(i,n) for(int i=0;i<(n);i++)
#define REP(i,n) for(int i=1;i<=(n);i++)
#define mod (ll)(1e9+7)
#define inf (ll)(3e18+7)
#define eps (double)(1e-9)
#define pi (double) acos(-1)
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
using namespace std;

using mint = modint998244353;

void solve() {
    ll a, n;
    cin >> n >> a;

    if(a == 1) {
        mint ans = 0;
        ans += n * (n-1) / 2;
        cout << ans.val() << endl;
        return;
    }

    mint ans = 0;
    mint now = 0;
    while(n >= a) {
        mint m = n - n / a;
        ans += m * (m - 1) / 2;
        ans += m * now;
        now += n%a + 1;

        n /= a;
    }

    ans += mint(n) * (n-1) / 2;
    ans += n * now;

    cout << ans.val() << endl;
}
int main() {
    int t;
    cin >> t;
    while(t--)solve();
}