package main

import . "fmt"

func main() {
	var n int
	Scan(&n)
	a := make([]int, n)
	for i := range a[:n-1] {
		Scan(&a[i])
	}
	var ans, p int
	for i := 0; i < n; i++ {
		var b, c int
		Scan(&b,&c)
		p += c - b
		ans += p * a[i]
	}
	Println(ans)
}