def solve():
    a, b, k = map(int, input().split())
    ans = []
    for i in range(1, 101):
        if a % i == 0 and b % i == 0:
            ans.append(i)
    print(ans[-k])


if __name__ == '__main__':
    solve() def solve():
    a, b, k = map(int, input().split())
    ans = []
    for i in range(1, 101):
        if a % i == 0 and b % i == 0:
            ans.append(i)
    print(ans[-k]) solve a, b, k = map(int, input().split()) a map(int, input().split()) map int input().split() ().split () input split b k ans = [] ans [] for i in range(1, 101):
        if a % i == 0 and b % i == 0:
            ans.append(i)
     i range(1, 101) range 1 101 if a % i == 0 and b % i == 0:
            ans.append(i)
     a % i == 0 and b % i == 0 a % i == 0 a % i a i 0 b % i == 0 b % i b i 0 ans.append(i) ans.append ans append i print(ans[-k]) print ans[-k] ans -k k if __name__ == '__main__':
    solve() __name__ == '__main__' __name__ '__main__' solve() solve def solve():
    a, b, k = map(int, input().split())
    ans = []
    for i in range(1, 101):
        if a % i == 0 and b % i == 0:
            ans.append(i)
    print(ans[-k]) def solve():
    a, b, k = map(int, input().split())
    ans = []
    for i in range(1, 101):
        if a % i == 0 and b % i == 0:
            ans.append(i)
    print(ans[-k]) solve
def solve():
    a, b, k = map(int, input().split())
    ans = []
    for i in range(1, 101):
        if a % i == 0 and b % i == 0:
            ans.append(i)
    print(ans[-k])


if __name__ == '__main__':
    solve()
