import math

N = int(input())
ans = ""
chs = [chr(ord('a') + i) for i in range(26)]
ci = 0

while N > 0:
    sqrt = int(math.sqrt(N))
    len = sqrt * 2 - 1
    for i in range(len):
        ans += chs[ci + i % 2]
    ci += 2
    N -= sqrt * sqrt

print(ans)