func main()
	var n: int :: cui@inputInt()
	var ans: int :: 0
	var idx: int :: 0
	for i(0, n - 1)
		var b: int :: cui@inputInt()
		for(1, b)
			do ans :+ (idx - i).abs()
			do idx :+ 1
		end for
	end for
	do cui@print("\{ans}\n")
end func