import math

def make_divisors(n):
    #https://qiita.com/LorseKudos/items/9eb560494862c8b4eb56
    lower_divisors , upper_divisors = [], []
    i = 1
    while i*i <= n:
        if n % i == 0:
            lower_divisors.append(i)
            if i != n // i:
                upper_divisors.append(n//i)
        i += 1
    return lower_divisors + upper_divisors[::-1]

a,b,k = map(int,input().split())
tmp = math.gcd(a,b)
ans = make_divisors(tmp)
print(ans[-k]) import math math def make_divisors(n):
    #https://qiita.com/LorseKudos/items/9eb560494862c8b4eb56
    lower_divisors , upper_divisors = [], []
    i = 1
    while i*i <= n:
        if n % i == 0:
            lower_divisors.append(i)
            if i != n // i:
                upper_divisors.append(n//i)
        i += 1
    return lower_divisors + upper_divisors[::-1] make_divisors lower_divisors , upper_divisors = [], [] lower_divisors [] upper_divisors [] i = 1 i 1 while i*i <= n:
        if n % i == 0:
            lower_divisors.append(i)
            if i != n // i:
                upper_divisors.append(n//i)
        i += 1
     i*i <= n i*i i i n if n % i == 0:
            lower_divisors.append(i)
            if i != n // i:
                upper_divisors.append(n//i)
         n % i == 0 n % i n i 0 lower_divisors.append(i) lower_divisors.append lower_divisors append i if i != n // i:
                upper_divisors.append(n//i)
         i != n // i i n // i n i upper_divisors.append(n//i) upper_divisors.append upper_divisors append n//i n i i += 1 i 1 return lower_divisors + upper_divisors[::-1] lower_divisors + upper_divisors[::-1] lower_divisors upper_divisors[::-1] upper_divisors ::-1 -1 n n a,b,k = map(int,input().split()) a map(int,input().split()) map int input().split() ().split () input split b k tmp = math.gcd(a,b) tmp math.gcd(a,b) math.gcd math gcd a b ans = make_divisors(tmp) ans make_divisors(tmp) make_divisors tmp print(ans[-k]) print ans[-k] ans -k k a,b,k = map(int,input().split()) map(int,input().split()) a k = map(int,input().split()) map(int,input().split()) k tmp = math.gcd(a,b) math.gcd(a,b) tmp b,k = map(int,input().split()) map(int,input().split()) b ans = make_divisors(tmp) make_divisors(tmp) ans def make_divisors(n):
    #https://qiita.com/LorseKudos/items/9eb560494862c8b4eb56
    lower_divisors , upper_divisors = [], []
    i = 1
    while i*i <= n:
        if n % i == 0:
            lower_divisors.append(i)
            if i != n // i:
                upper_divisors.append(n//i)
        i += 1
    return lower_divisors + upper_divisors[::-1] def make_divisors(n):
    #https://qiita.com/LorseKudos/items/9eb560494862c8b4eb56
    lower_divisors , upper_divisors = [], []
    i = 1
    while i*i <= n:
        if n % i == 0:
            lower_divisors.append(i)
            if i != n // i:
                upper_divisors.append(n//i)
        i += 1
    return lower_divisors + upper_divisors[::-1] make_divisors
import math

def make_divisors(n):
    #https://qiita.com/LorseKudos/items/9eb560494862c8b4eb56
    lower_divisors , upper_divisors = [], []
    i = 1
    while i*i <= n:
        if n % i == 0:
            lower_divisors.append(i)
            if i != n // i:
                upper_divisors.append(n//i)
        i += 1
    return lower_divisors + upper_divisors[::-1]

a,b,k = map(int,input().split())
tmp = math.gcd(a,b)
ans = make_divisors(tmp)
print(ans[-k])