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