#yuki254
s='abcdefghijklmnopqrstuvwxyz'
n=int(raw_input())
def f(n,s):
 if n<=1:
  return 'z'*n
 m=int((n+0.25)**0.5-0.5)
 return s[0:2]*m+f(n-m*(m+1),s[2:])
print f(n,s)