# Arup Guha
# 12/11/2024
# Solution to UCF HS Online Div 2 Problem: Palindromic Passwords

# Get input.
n = int(input())

# Store triangular numbers here upto n
tri = [1]
add = 2

# Keep on going.
while tri[-1] < n:

    # Get to next tri number.
    cur = tri[-1] + add
    tri.append(cur)
    add += 1

# Easier this way.
trilen = len(tri)

# Initialize variables.
curLet = 0
curCnt = n
res = ""

# Go backwards through array.
for i in range(trilen-1,-1,-1):

    # We can do i+1 letters in a row.
    if curCnt >= tri[i]:
        curCnt -= tri[i]
        res = res + ( (chr(curLet+ord('a')))*(i+1) )
        curLet = (curLet+1)%26

# This is the only case where we don't finish.
if curCnt == 1:
    res = res + (chr(curLet+ord('a')))

# Ta da!
print(res)