N = input()

N_to_alpha = dict()
for i in xrange(0, 27):
    N_to_alpha[i] = chr(i+65)

digits = []
for i in range(9)[::-1]:
    digit = N / (26**i)
    digits.append(digit)
    if digit > 0:
        N %= (26**i)


while digits[0] == 0 and len(digits) > 1:
    del digits[0]

digits[0] -= 1

string = [N_to_alpha[d] for d in digits]

ans = ''.join(string)
print ans