def func(K,n):
    return (K**n-1)/(K-1)

def func_bisect(K,N):
    left = 1
    right = 10
    eps = 0.1
    while left < right:
        mid = (left+right)/2
        #print(func(K,mid),left,mid,right)
        if abs(N -func(K,mid)) < eps:
            return mid
        elif N -func(K,mid) > eps:
            left = mid
        elif func(K,mid) - N > eps:
            right = mid

Q = int(input())
for i in range(Q):
    N,K = map(int,input().split())
    if K == 1:
        print(N-1)
    else:
        print(int(func_bisect(K,N)))