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

#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define ALL(v) v.begin(),v.end()
typedef long long ll;
template <class T> using V=vector<T>;
template <class T> using VV=V<V<T>>;

const int MOD=998244353;
const ll m2=499122177;
ll f(ll x){
  x%=MOD;
  return x*(x+1)%MOD*m2%MOD;
}
 
int main(){
  ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  
  int t;
  cin>>t;
  while(t--){
    ll n,a;
    cin>>n>>a;
    if(a==1){
      cout<<f(n-1)<<'\n';
      continue;
    }
    ll now=n,ans=0,sum=0,j=0;
    while(1){
      ll nex=now/a;
      ans=(ans+f(now-nex-1))%MOD;
      ll cnt=now-nex;
      ans=(ans+cnt*sum%MOD+cnt*j%MOD)%MOD;
      sum=(sum+now-nex*a)%MOD;
      if(nex==0) break;
      now=nex;
      j++;
    }
    cout<<ans<<'\n';
  }
    
  return 0;
}