def alphabet(N):
    N = N + 1
    M = N
    p = 1
    n = 1
    while True:
        if M - (26 ** p) > 0:
            M = M - (26 ** p)
            p += 1
        else:
            break
    p -= 1
    li = [0 for i in range(p + 1)]
    for l in range(len(li)):
        bef = 0
        for x in range(p - l):
            bef += 26 ** x
        for n in range(1, 28):
            if (l == len(li) - 1) and (N - n * (26 ** (p - l)) == 0):
                li[l] = 0 + n
                break
            elif N - n * (26 ** (p - l)) < bef:
                n = n - 1
                li[l] = 0 + n
                N = N - n * (26 ** (p - l))
                break
    S = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
    ans = ''
    for j in range(len(li)):
        ans = ans + S[li[j] - 1]
    return ans

def main():
    N = int(input())
    print(alphabet(N))

if __name__ == '__main__':
    main()