import string
N=int(input())
if N==0:
    print('A')
    exit()
ret=""
alp=list(string.ascii_uppercase)
cnt=0
while N:
    if not cnt:
        ret+=alp[N%26]
    else:
        ret+=alp[(N-1)%26]
    cnt+=1
    N=N//26
ret=ret[::-1]
print(ret)