from math import gcd

def make_divisors(n):
    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())
x = gcd(a, b)
l = make_divisors(x)
print(l[-k]) from math import gcd def make_divisors(n):
    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 x = gcd(a, b) x gcd(a, b) gcd a b l = make_divisors(x) l make_divisors(x) make_divisors x print(l[-k]) print l[-k] l -k k k = map(int, input().split()) map(int, input().split()) k b, k = map(int, input().split()) map(int, input().split()) b def make_divisors(n):
    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):
    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 a, b, k = map(int, input().split()) map(int, input().split()) a x = gcd(a, b) gcd(a, b) x l = make_divisors(x) make_divisors(x) l
from math import gcd

def make_divisors(n):
    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())
x = gcd(a, b)
l = make_divisors(x)
print(l[-k])