import sys
input = sys.stdin.buffer.readline
sys.setrecursionlimit(10 ** 7)
Q = int(input())
ans = [-1] * Q
for i in range(Q):
    n, k = map(int, input().split())
    if k == 1:
        ans[i] = n - 1
        continue
    cnt = 0
    while n > 1:
        n = (n + k - 2) // k
        cnt += 1
    ans[i] = cnt

print(*ans, sep="\n")