p=998244353

def decomp(num,base):
    result=[]
    while num:
        num,res=divmod(num,base)
        result.append(res)
    return result[::-1]

for _ in range(int(input())):
    n,a=map(int,input().split())
    if a==1:
        print((n*(n-1)//2)%p)
        continue
    coeffs=decomp(n,a)
    answer=0
    tmp=0
    for i in range(len(coeffs)):
        upper=n//a**(len(coeffs)-i-1)
        constant=upper+sum(coeffs[i+1:])+len(coeffs)-i-1
        answer+=constant*(upper-tmp)-upper*(upper+1)//2+tmp*(tmp+1)//2
        answer%=p
        tmp=upper
    print(answer)