def num2ALPHABET(num: int) -> str:
    return chr(65+num)


def main():
    N = int(input())
    if not N:
        print("A")
        return
    base26 = []
    while N:
        base26.append(N % 26)
        N //= 26
    base26.reverse()
    if len(base26) == 1:
        print(num2ALPHABET(base26[0]))
    else:
        print(num2ALPHABET(base26[0]-1) +
              "".join(map(num2ALPHABET, base26[1:])))


if __name__ == "__main__":
    main()