import sys

def II(): return int(sys.stdin.readline())

def main():
    n=II()
    if n==1:
        print("a")
        exit()
    ans=""
    i=97
    while n>1:
        ans+=chr(i)
        if n&1:
            n-=1
            i+=1
            if i==123:i=97
        else:
            n>>=1
    print(ans+ans[::-1])

main()