Q = int(input())

def S(r, n):
    if r == 1:
        return n+1
    return (pow(r, n+1)-1)//(r-1)

for _ in range(Q):
    N,K = map(int, input().split())
    l = 0
    r = N+1
    while r-l > 1:
        m = (r+l)//2
        if S(K, m) < N:
            l = m
        else:
            r = m
    if S(K, l) >= N:
        ans = l
    else:
        ans = r
    print(ans)