def solution(s, skip, index):
answer = ''
alpha = [chr(i) for i in range(97,123)]*3
for i in s:
ss = alpha.index(i)
fin = ss+index
ls = alpha[ss:fin+1] #원래 도착
while True:
a = 0
for j in ls:
if j in skip:
ls.remove(j)
fin += 1
ls.append(alpha[fin])
a = 1
break
if a == 0:
answer += ls[-1]
break
return answer