# Torbert, 9.12.2007

def count_diff_0(a,b)
	return -1 if a.length != b.length
	count=0
	for k in 0...a.length do
		count+=1 if a[k] != b[k]
	end
	return count
end

def count_diff_1(a,b)
	return -1 if a.length != b.length
	count=0
	# puts a.split("").zip(b.split("")).inspect
	for k,j in a.split("").zip(b.split("")) do
		count+=1 if k!=j
	end
	return count
end

def count_diff(a,b)
	return -1 if a.length != b.length
	c=a.split("").zip(b.split("")).map{ |k| k.uniq }.delete_if{ |k| k.length==1 }
	# puts c.inspect
	return c.length
end

puts count_diff( "hello","world" )
puts count_diff( "hello","there" )
puts count_diff( "talk" ,"balk"   )
puts count_diff( "talk" ,"bale"   )
puts count_diff( "talk" ,"pale"   )
puts count_diff( "talk" ,"pole"   )
puts count_diff( "talk" ,"pose"   )

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