1. d~~~~[

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flag=[False]*26
for k in range(i,j+1):
if flag[ord(s[k])-ord("a")]==False:
flag[ord(s[k])-ord("a")]=True
else:
return False
return True

s=input() maxlen=0 for i in range(0,len(s)): j=i+1 while j<len(s) and pd(i,j)==True: j+=1 if j-i>maxlen: maxlen=j-i pos=i print(s[pos:pos+maxlen])