N = input()

N_to_alpha = dict()
for i in xrange(0, 27):
    N_to_alpha[i] = chr(i+64)

i = 0
while True:
    if (26**i)-1 <= N < 26**(i+1):
        digit = i+1
        break
    else:
        i += 1

ans = []
j = 1
for _ in xrange(i):
    k = N / (26**(digit-j))
    N -= k * (26**(digit-j))
    j += 1
    ans.append(N_to_alpha[k])
else:
    ans.append(N_to_alpha[N+1])

print ''.join(ans)