N=int(input())

ANS=[]
c=0
while N>0:
    for i in range(10**6):
        if i*(i+1)//2<=N:
            plus=i
        else:
            break
    ANS+=[c]*plus
    N-=plus*(plus+1)//2
    c+=1

ANS=[chr(ANS[i]+97) for i in range(len(ANS))]

print("".join(ANS))