import sys
readline=sys.stdin.readline

N=int(readline())
alp=[chr(i) for i in range(97,97+26)]
ans=[]
for n in range(33000,0,-1):
    if n*n<=N:
        a,b=alp.pop(),alp.pop()
        ans.append(a+(b+a)*(n-1))
        N-=n*n
print(*ans,sep="")