if __name__ == '__main__':
    n = int(input().strip())
    
    nums = [i for i in range(1, n+1) if n%i==0]
    best = 0
    max_sum = 0
    for x in nums:
        soma = sum(map(int,str(x)))
        if soma > max_sum:
            best, max_sum = x, soma
        elif soma == max_sum:
            best = min(x, best)
    
    print(best)