package main

import . "fmt"
import . "os"
import bf "bufio"

func main() {
	rd:=bf.NewReader(Stdin)
	var n,x int64
	Fscan(rd,&n,&x)
	x=-x*(n-1)
	for ;n>0;n-- {
		var c int64
		Fscan(rd,&c)
		x+=c
	}
	Println(x)
}