func main()
	var n: int :: cui@inputInt()
	var ans: int :: 0
	var a: []int :: #[n - 1]int
	var b: []int :: #[n - 1]int
	for i(0, n - 2)
		do a[i] :: cui@inputInt()
		do b[i] :: cui@inputInt()
	end for
	
	var sumIn: int :: 0
	var sumOut: int :: 0
	for i(0, n - 2)
		do sumIn :+ a[i]
		do sumOut :+ b[i]
	end for
	if(sumIn < sumOut)
		var t: []int :: ##a
		do a :: ##b
		do b :: ##t
		var sumT: int :: sumIn
		do sumIn :: sumOut
		do sumOut :: sumT
	end if
	
	var maxOut: int :: sumIn
	var minOut: int :: sumIn - sumOut
	for i(0, n - 2)
		var sum: int :: 0
		for j(0, n - 2)
			if(i <> j)
				do sum :+ b[j]
			end if
		end for
		do minOut :: [minOut, a[i] - sum].max()
	end for
	do ans :: maxOut - minOut + 1
	do cui@print("\{ans}\n")
end func