def conv(n):
    ans = chr(n % 26 + 65)
    while n >= 26:
        n = n // 26 - 1
        ans += chr(n % 26 + 65)
    return ans[::-1]


def main():
    n = int(input())
    print(conv(n))
    
if __name__ == '__main__':
    main()