import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################

inf = 10 ** 18 + 100
def naive(n, a):
    dp = [inf] * (n + 1)
    dp[n] = 0
    for i in range(n-1, 0, -1):
        if i * a <= n:
            dp[i] = min(dp[i], dp[i*a] + 1)
        dp[i] = min(dp[i], dp[i+1] + 1)
    
    # print(dp[1:])
    for i in range(1, n + 1):
        print(i, dp[i])
    x = n // a
    while x > 0:
        # print(x, dp[x])
        x //= a
    return sum(dp[1:])

mod = 998244353
def solve(n, a):
    if a == 1:
        return (n * (n - 1) // 2) % mod
    ans = 0
    x = 0
    while n:
        m = n // a
        ans += (n - m) * (x * 2 + n - m - 1) // 2 
        ans %= mod
        x += 1 + n % a
        n = m
    return ans

for _ in range(ni()):
    n, a = na()
    # print(naive(n, a))
    print(solve(n, a))