# coding: utf-8
# Your code here!
def solv1():
    n=int(input())
    
    a=[[]for i in range(n)]
    a[0]=[[0]]
    
    for i in range(n-1):
        b=[]
        for pa in a[i]:
    #        print(pa)
            el=[j for j in set(pa)]
    #        print(el)
            el.append(max(pa)+1)
            for l in el:
                b+=[pa+[l]]
    #    print(i,b)
        a[i+1]=b
    ans=[]
    for i in a:
        ans+=i
        #print(i)
    ans=sorted(ans)
    for i in ans:
        print(''.join([chr(j+97) for j in i]))

solv1()
