N=int(input())

ans=""
def keisan(n_i):
    n=n_i//26  
    make_ans(n_i)
    if n>=1:
        keisan(n-1)
    return 0

def make_ans(n):
    global ans
    ans=ans+chr(0x41+int(hex(n%26)[2:],16))

keisan(N)
print(ans[::-1])