N = int(input()) + 1
alphabets = [chr(i) for i in range(ord('A'), ord('A') + 26)]

if N <= 26:
    print(alphabets[N - 1])
    exit()


def encode_x_base(n, x):
    if n == 0:
        return [0]

    ret = []
    while n:
        ret.append(n % x)
        n //= x

    return ret[::-1]


encoded_N_26_based = encode_x_base(N // 26, 26)
ans = [alphabets[i - 1] for i in encoded_N_26_based] + [alphabets[N % 26 - 1]]
print(''.join(ans))