e

n=int(input())
list1 = []
for i in range(1,n+1):
if n % i 0:
list1 .append(i)
def ispri(num):
if num <=1:
return 0
for i in range(2,num):
if num % i0:
return 0
return 1
list2=[]
for num in list1:
if ispri(num)==1:
list2.append(num)
print(max(list2))