n = int(input())
a = n
table = set()
i = 2

while i * i <= n:
    while n % i == 0:
        n = n // i
        table.add(i)
    i += 1
if n > 1:
    table.add(n)
    
ans = sorted(list(table))
# print(ans)
if len(ans) >= 2:
    if ans[0] == 2:
        if a % 4 == 0 and ans[1] != 3:
            print(4)
        else:
            print(ans[1])
    else:
        print(ans[1])
else:
    print([4, ans[0]][ans[0]!=2])