def search(k, cost, visited, ans):
    while k < cost[0][1]:
        cost = cost[1:]
    if k in visited:
        return False
    visited.add(k)
    for i, c in cost:
        ans.append(i)
        if k == c:
            return True
        else:
            if search(k - c, cost, visited, ans):
                return True
            ans = ans[:-1]

if __name__ == "__main__":
    k = input()
    cost = [0]
    
    for i in xrange(1, 350):
        if cost[-1] + i - 1 > k:
            break
        cost.append(cost[-1] + i - 1)

    visited = set()
    ans = []
    ans_str = ''
    if search(k, list(reversed(list(enumerate(cost)))), visited, ans):
        for i, count in enumerate(ans):
            ans_str += chr(ord('a') + i) * count
    print ans_str
