sum=26
count=0
n = int(input())
k = ord('a')-1
while(sum<n) :
  count+=1
  sum+=26**(count+1)

current=n
mozi=''
mozi1=''
for i in range(count+1) :
  mozi+='z'
if current==sum :
  print(mozi)
else :
  for i in reversed(range(count+1)) :
    c=current//26**i

    mozi1+=chr(c+k)
    current = current % 26 ** i
  print(mozi1)