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

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