def c_s(s,i):
	return [chr(s+(j&1)) for j in range(2*i-1)]
N = int(raw_input())
M = 1<<15
C = [i**2 for i in xrange(M)]
for i in xrange(1,M):
	if C[i+1] <= N:
		continue
	ans = c_s(97,i)
	rest = N - C[i]
	for j in range(1,rest+1):
		if C[j+1] <= rest:
			continue
		ans += c_s(99,j) + [chr(101+(k%22)) for k in xrange(rest-C[j])]
		break
	print "".join(ans)
	break