N=int(input())

S = 'abcdefghij'

def num(x):
    ans = 0
    for i in range(len(S)):
        count = 0
        for j in range(0,len(x)):
            if x[j] == S[i]:
                count = count +1
        if count != 0:
            ans = ans + 1
        else:
            ans = ans
    return ans

def base(x):
    List=[]
    for j in range(len(x)):
        for i in range(num(x[j])+1):
            List.append(x[j]+S[i])
    return List

K = 'a'

cou = 1
while cou < N:
    K = base(K)
    cou = cou+1

print(K)