MOD = 998244353
INV2 = (MOD + 1) // 2

def solve(n, a):
    if a == 1:
        return (n * (n - 1) * INV2) % MOD

    total = 0
    m_prev = n
    s_prev = 0

    while m_prev > 0:
        r, m = m_prev % a, m_prev // a

        d = (m_prev - m) % MOD
        total += d * s_prev + (d * (d - 1)) % MOD * INV2
        total %= MOD

        s_prev += r + 1
        m_prev = m

    return total

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