func main()
	var n: int :: cui@inputInt()
	var a: []int :: #[n]int
	for i(0, n - 1)
		do a[i] :: cui@inputInt()
	end for
	
	var ans: int :: 0
	for i(0, n - 1)
		var l: int :: i + 1
		var r: int :: n - i
		do ans :+ a[i] * (l * r)
	end for
	do cui@print("\{ans}\n")
end func