N = int(input())
ans = []

def f(x):
    yes = 0
    no = 10 ** 5
    while no - yes != 1:
        mid = (yes + no)//2
        if mid * (mid + 1)//2 <= x:
            yes = mid
        else:
            no = mid
    return yes

now = 0
while N:
    M = f(N)
    N -= M * (M + 1)//2
    ans.extend([chr(now + ord("a"))] * M)
    now += 1

print(*ans, sep="")