import sys
input = sys.stdin.readline

mod=998244353

def calc(N,A):
    DP=[1<<60]*(N+1)

    DP[N]=0

    for i in range(N,-1,-1):
        if i%A==0:
            DP[i//A]=min(DP[i//A],DP[i]+1)
        if i-1>=0:
            DP[i-1]=min(DP[i-1],DP[i]+1)

    return DP

T=int(input())
for tests in range(T):
    N,A=map(int,input().split())

    LIST=[(N,0)]

    now=N
    kai=0
    while now>1:
        k=now%A

        LIST.append(((now-k)//A,kai+k+1))
        now=(now-k)//A
        kai+=k+1
        
        
    ANS=0

    #print(LIST)

    for i in range(len(LIST)):
        if i<len(LIST)-1:
            a,b=LIST[i]
            c,d=LIST[i+1]

            ANS+=(b+(b+(a-c-1)))*(a-c)//2
            ANS%=mod

            #print(ANS)
        else:
            a,b=LIST[i]

            if a==1:
                ANS+=b
            else:
                pass

    print(ANS%mod)