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

long long mod = 998244353;
//入力が必ず-mod<a<modの時.
struct mint{
    long long v = 0;
    mint(){} mint(int a){v = a<0?a+mod:a;} mint(long long a){v = a<0?a+mod:a;}
    mint(unsigned long long a){v = a;}
    long long val(){return v;}

    mint &operator=(const mint &b) = default;
    mint operator-() const {return mint(0)-(*this);}
    mint operator+(const mint b){return mint(v)+=b;}
    mint operator-(const mint b){return mint(v)-=b;}
    mint operator*(const mint b){return mint(v)*=b;}
    mint operator/(const mint b){return mint(v)/=b;}

    mint operator+=(const mint b){
        v += b.v; if(v >= mod) v -= mod;
        return *this;
    }
    mint operator-=(const mint b){
        v -= b.v; if(v < 0) v += mod; 
        return *this;
    }   
    mint operator*=(const mint b){v = v*b.v%mod; return *this;}
    mint operator/=(mint b){
        if(b == 0) assert(false);
        int left = mod-2;
        while(left){if(left&1) *this *= b; b *= b; left >>= 1;}
        return *this;
    }

    mint operator++(){*this += 1; return *this;}
    mint operator--(){*this -= 1; return *this;}
    mint operator++(int){*this += 1; return *this;}
    mint operator--(int){*this -= 1; return *this;}
    bool operator==(const mint b){return v == b.v;}
    bool operator!=(const mint b){return v != b.v;}
    bool operator>(const mint b){return v > b.v;}
    bool operator>=(const mint b){return v >= b.v;}
    bool operator<(const mint b){return v < b.v;}
    bool operator<=(const mint b){return v <= b.v;}

    mint pow(long long n){
        mint ret = 1,p = v;
        if(n < 0) p = p.inv(),n = -n;
        while(n){
            if(n&1) ret *= p;
            p *= p; n >>= 1;
        }
        return ret;
    }
    mint inv(){return mint(1)/v;}
};

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

    int T; cin >> T;
    mint div2 = mint(1)/2;
    while(T--){
        long long N,A; cin >> N >> A;
        if(A == 1){
            mint ans = N%mod;
            ans *= (N-1)%mod;
            ans *= div2;
            cout << ans.v << "\n"; continue;
        }

        mint answer = 0;
        long long R = N,pa = 1,n = 0;
        while(true){
            long long L = 1;
            if((__int128_t)pa*A <= N) L = N/(pa*A)+1;
            answer += (R-L+1)%mod*n%mod;
            long long l = N-R*pa,r = N-L*pa,v = l;
            for(int i=0; i<n; i++){
                answer += (R-L+1)%mod*(v%A%mod)%mod;
                v /= A; l /= A; r /= A;
            }
            answer += div2*((R-L)%mod)*((R-L+1)%mod);
            if(L == 1) break;
            R = L-1; pa *= A; n++;
        }   
        cout << answer.v << "\n";
    }
}