# please use positive value
def convertDecimal(
            num, \
            decimal, \
            characters = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ", \
            lowercharacter=False \
    ):
    
    # decimal only can use 2 to 36
    if num <= 0 and not 2 <= decimal <= 36:
        return None

    ret = ""
    while num > 0:
        ret = characters[num % decimal] + ret
        num //= decimal
    return ret

def solve(num):
    cnt = 1
    while num > 26 ** cnt:
        num -= 26 ** cnt
        cnt += 1
    return convertDecimal(num, 26, "ABCDEFGHIJKLMNOPQRSTUVWXYZ")

if __name__=="__main__":
    print(solve(int(input())))