mod = 998244353

def digsum(n,a):
    res = 0
    while n > 0:
        res += n % a
        n //= a
    return res

def solve(n,a):
    if a == 1:
        return (n * (n - 1) // 2) % mod
    k,power,ans = 0,1,0
    while power <= n:
        f = (n // power) + digsum(n % power,a) + k
        f %= mod
        ans += f * ((n // power) - n // (power * a))
        ans %= mod
        power *= a
        k += 1
    ans -= (n * (n + 1) // 2) % mod
    return (ans + mod) % mod

t = int(input())
for _ in range(t):
    n, a = map(int, input().split())
    print(solve(n,a))