n=int(input())

ANS=[]
while n>0:
    x=n%26
    ANS+=[x]
    n//=26

if ANS==[]:
    ANS=[0]
    
for i in range(len(ANS)):
    if i==0:
        ANS[i]=chr(ANS[i]+65)
    else:
        ANS[i]=chr(ANS[i]+64)

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