N = int(eval(input())) - 1

rst = ''



for i in range(1, 15):

    if N >= 26 ** i:

        N -= 26 ** i

        continue

    for j in range(i):

        rst += chr(ord('a') + N % 26)

        N //= 26

    print((rst[::-1]))

    break
N = int(eval(input())) - 1

rst = ''

for i in range(1, 16):

    if N >= 26 ** i:

        N -= 26 ** i

        continue

    for j in range(i):

        rst += chr(ord('a') + N % 26)

        N //= 26

    print((rst[::-1]))

    break
N = int(eval(input())) - 1
rst = ""
for i in range(1, 15):
    if N >= 26**i:
        N -= 26**i
        continue
    for j in range(i):
        rst += chr(ord("a") + N % 26)
        N //= 26
    print((rst[::-1]))
    break

N = int(eval(input())) - 1
rst = ""
for i in range(1, 16):
    if N >= 26**i:
        N -= 26**i
        continue
    for j in range(i):
        rst += chr(ord("a") + N % 26)
        N //= 26
    print((rst[::-1]))
    break

-for i in range(1, 15): +for i in range(1, 16):