def calc(N,x): if N==0: return [] if N==1: return [x] if N%2==1: return [x]+calc(N-1,x+1) two=0 k=N while k%2==0: two+=1 k//=2 if k==1: return [x]*(two) else: return [x]*(two+1)+calc(k-1,x+1) N=int(input()) if N==1: print("a") else: ANS=calc(N,1) ANS=ANS+ANS[::-1] for i in range(len(ANS)): ANS[i]=chr(ANS[i]%26+97) print("".join(ANS))