func main()
	var n: int :: cui@inputInt()
	var ans: int :: 0
	if(n = 2)
		do ans :: 1
	else
		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 maxOut: int :: sumIn
			var minOut: int :: sumIn - sumOut
			do ans :: maxOut - minOut + 1
		else
			var maxIn: int :: sumOut
			var minIn: int :: sumOut - sumIn
			do ans :: maxIn - minIn + 1
		end if
	end if
	do cui@print("\{ans}\n")
end func