def divisors(n):
    divs = []
    for d in range(1, int(n**0.5) + 1):
        if n % d == 0:
            divs.append(d)
            q = n // d
            if q != d:
                divs.append(q)
    divs.sort()
    return divs

N = int(input())
divs = divisors(N)
ans = -1
for d in divs:
    if d > 2:
        ans = d
        break
print(ans)