#!/bin/bash

script=:1
for l in {a..z}
do
	script+=";s/$l${l^}//g;s/${l^}$l//g"
done

polymer=$(<input.txt)
shortest=${#polymer}

for l in {a..z}
do
	shrunk=$(sed "s/[${l^}$l]//g;$script;t1" input.txt)
	length=${#shrunk}
	((length<shortest)) && shortest=$length
done

echo $shortest