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

const int iinf = 1e9;
const ll inf = 1e18;
template<ll mod>
struct Mint {
    using M=Mint; ll v;
    M& put(ll x) { v=(x<mod)?x:x-mod; return *this; }
    Mint(ll x=0) { put(x%mod+mod); }
    M operator+(M m) {return M().put(v+m.v);}
    M operator-(M m) {return M().put(v+mod-m.v);}
    M operator*(M m) {return M().put(v*m.v%mod);}
    M operator/(M m) {return M().put(v*m.inv().v%mod);}
    M operator+=(M m) { return put(v+m.v); }
    M operator-=(M m) { return put(v+mod-m.v); }
    M operator*=(M m) { return put(v*m.v%mod); }
    M operator/=(M m) { return put(v*m.inv().v%mod); }
    bool operator==(M m) { return v==m.v; }
    M pow(ll m) const {
        M x=v, res=1;
        while (m) {
            if (m&1) res=res*x;
            x=x*x; m>>=1;
        }
        return res;
    }
    M inv() { return pow(mod-2); }
};
template<ll mod>
ostream&operator<<(ostream&o,Mint<mod>v){return o<<v.v;}


template<typename T>
ostream& operator<<(ostream &o, vector<T> v) {
    for (int i = 0; i < v.size(); i++)
        o << v[i] << (i+1<v.size()?" ":"");
    return o;
}
template <typename T>
struct SegTree {
    using F = function<T(T, T)>;
    int n;
    F f;
    T ti;
    vector<T> dat;
    SegTree() {}
    SegTree(F f, T ti,int num) : f(f), ti(ti) {
        n = max(__bit_ceil(num), 1);
        dat.assign(n << 1, ti);
    }
    SegTree(F f,T ti,vector<T>&v):SegTree(f,ti,v.size()){
        for (int i = 0; i < v.size(); i++)
            dat[n + i] = v[i];
        for(int i=n-1;i;i--) dat[i]=f(dat[i*2], dat[i*2+1]);
    }
    void set_val(int k, T x) {
        dat[k += n] = x;
        while(k >>= 1) dat[k] = f(dat[k*2], dat[k*2+1]);
    }
    T query(int a, int b) {
        if (a >= b) return ti;
        T vl = ti, vr = ti;
        for (int l=a+n, r=b+n; l<r; l>>=1, r>>=1) {
            if (l & 1) vl = f(vl, dat[l++]);
            if (r & 1) vr = f(dat[--r], vr);
        }
        return f(vl, vr);
    }
};
struct Edge { int to; ll cost; };

const int MOD = 998244353;

// a^e mod
ll modpow(ll a, ll e=MOD-2){
    ll r=1;
    while(e){
        if(e&1) r=r*a%MOD;
        a=a*a%MOD;
        e>>=1;
    }
    return r;
}

using mint = Mint<MOD>;
mint sm(mint n) {
    return n * (n+1) / 2;
}
mint sm(mint l, mint r) {
    return sm(r) - sm(l);
}

int main() {
    cin.tie(0)->sync_with_stdio(false);
    int t;
    cin >> t;
    while (t--) {
        ll n, a;
        cin >> n >> a;
        ll m = n;
        mint ans = 0;
        mint sub = 0;
        while (true) {
            ll l = m / a + 1;
            ll r = m;
            if (l > r) break;
            // cout << l << " " << r << " "  << sub <<" " <<(sm(mint(r-l)) + mint(r-l+1)*sub)<< endl;
            ans += sm(mint(r-l)) + mint(r-l+1)*sub;
            sub += m % a + 1;
            m /= a;
        }
        cout << ans << endl;
    }
    return 0;
}