#2501 - python 약수 구하기

약수 구하기

N,K = map(int,input().split())
cnt = 0
flag = 0
for i in range (1,N+1):
    if ( N % i == 0):
        tmp = i
        cnt+=1
    if (cnt == K):
        print (i)
        flag = 0
        break
    elif (cnt < K):
        flag = 1

if (flag == 1):
    print(0)