def checker(n):
    if n == 1:
        return False
    i = 2
    while(i * i <= n):
        if n % i == 0:
            return True
        i += 1
    return False
        
n = int(input())

result = -1
for i in range(n - 100, n + 100 + 1):
    if checker(i):
        result = i
        break

print(result)