from string import ascii_lowercase

N = input()
S = ''
p = 0
alp = ascii_lowercase[1:]

while N > 0:
    i = 1
    while i <= N:
        S += 'a'
        N -= i
        i += 1
    if N > 0:
        S += alp[p]
        p = (p + 1) % 25
        N -= 1
        
print S