7-18 输出10个不重复的英文字母 (50分)

s = input() l = [] for i in s: if len(l) == 10: break if i.isalpha(): if (i.swapcase() not in l) and (i not in l): l.append(i) if len(l) != 10: print('not found') else: print(''.join(l))