import sys

sys.setrecursionlimit(10 ** 8)

input = sys.stdin.readline


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

    ans = []
    while N >= 0:
        ans.append(chr(ord("A") + N % 26))
        N = N // 26 - 1

    print("".join(ans[::-1]))


if __name__ == '__main__':
    main()