import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.NoSuchElementException;

public class Main implements Runnable {
    public static void main(String[] args) {
        new Thread(null, new Main(), "", 512 * 1024 * 1024).start();
    }
    
    final long mod=998244353;
    
    long pow(long a, long n) {
    	if(n==0)return 1;
    	return pow(a*a%mod,n/2)*(n%2==1?a:1)%mod;
    }
    
    long inv(long a) {
    	return pow(a,mod-2);
    }
    
    long i2=inv(2);
    
    long solve(long N, long A) {
    	if(A==1)return N%mod*(N-1)%mod*i2%mod;
    	long b=1;
    	int e=0;
    	while(b*A<=N) {
    		b*=A;
    		++e;
    	}
    	long[] x=new long[e+10];
    	long[] power=new long[e+10];
    	long[] res=new long[e+10];
    	x[0]=N;
    	power[0]=1;
    	for(int i=1;i<x.length;++i) {
    		x[i]=x[i-1]/A;
    	}
    	for(int i=0;i<x.length;++i)x[i]%=mod;
    	for(int i=1;i<power.length;++i) {
    		power[i]=power[i-1]*(A%mod)%mod;
    	}
    	for(int i=1;i<res.length;++i) {
    		res[i]=(res[i-1]+x[i-1]%A)%mod;
    	}
    	//x[i]=[N/A^i]
    	long ans=0;
    	for(int i=0;i<=e;++i) {
    		
    			// A^{e-i-1} <= [N/A^{i+1}] < z < A^{e-i} 
    		if(i!=e) {
				long d=(power[e-i]-x[i+1]-1)%mod;
				if(d>0) {
					ans+=d*(d+1)%mod*i2%mod;
					ans%=mod;
					ans+=d*(x[i]-power[e-i])%mod;
					ans%=mod;
					ans+=d*(i+res[i])%mod;
					ans%=mod;
				}
    		}
    		//A^{e-i} <= z <= [N/A^i] < A^{e-(i-1)}
    		
    		ans+=(x[i]-power[e-i])%mod*(x[i]-power[e-i]+1)%mod*i2%mod;
    		ans+=(i+res[i])*(x[i]-power[e-i]+1)%mod;
    		ans%=mod;
    	}
    	return (ans+mod)%mod;
    }
    
    public void run() {
    	FastScanner sc=new FastScanner();
    	PrintWriter pw=new PrintWriter(System.out);
    	int T=sc.nextInt();
    	for(int t=0;t<T;++t) {
    		long N=sc.nextLong();
    		long A=sc.nextLong();
    		pw.println(solve(N,A));
    	}
    	//
//    	tr(solve(5,2));
    	pw.close();
    }
    
    void tr(Object...objects) {System.out.println(Arrays.deepToString(objects));}
}


class FastScanner {
	private final InputStream in = System.in;
	private final byte[] buffer = new byte[1024];
	private int ptr = 0;
	private int buflen = 0;
	private boolean hasNextByte() {
		if (ptr < buflen) {
			return true;
		}else{
			ptr = 0;
			try {
				buflen = in.read(buffer);
			} catch (IOException e) {
				e.printStackTrace();
			}
			if (buflen <= 0) {
				return false;
			}
		}
		return true;
	}
	private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
	private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
	public boolean hasNext() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++; return hasNextByte();}
	public String next() {
		if (!hasNext()) throw new NoSuchElementException();
		StringBuilder sb = new StringBuilder();
		int b = readByte();
		while(isPrintableChar(b)) {
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	public long nextLong() {
		if (!hasNext()) throw new NoSuchElementException();
		long n = 0;
		boolean minus = false;
		int b = readByte();
		if (b == '-') {
			minus = true;
			b = readByte();
		}
		if (b < '0' || '9' < b) {
			throw new NumberFormatException();
		}
		while(true){
			if ('0' <= b && b <= '9') {
				n *= 10;
				n += b - '0';
			}else if(b == -1 || !isPrintableChar(b)){
				return minus ? -n : n;
			}else{
				throw new NumberFormatException();
			}
			b = readByte();
		}
	}
	public int nextInt() {
		long nl = nextLong();
		if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) throw new NumberFormatException();
		return (int) nl;
	}
	public double nextDouble() { return Double.parseDouble(next());}
}