#!/usr/bin/python
from string import lowercase as lo
from itertools import izip_longest

def nya(n, i, cat):
    if n == 0:
        return cat
    sq = int(n ** .5)
    l = 2*sq - 1
    a, b = lo[i], lo[-i-1]
    x, y = l/2+1, l/2
    return nya(n-sq*sq, (i+1)%N, cat+''.join(map(''.join, izip_longest(a*x, b*y, fillvalue=''))))

n = int(raw_input())
N = len(lo)
print nya(n, 0, '')