package main

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

func main() {
	rd := bf.NewReader(Stdin)
	var n, a int
	Fscan(rd, &n, &a)
	plus, minus := -a, 0
	hasMinus := false
	for i := 1; i < n; i++ {
		Fscan(rd, &a)
		if hasMinus {
			plus, minus = max(plus, minus-a, -a), max(minus, plus+a)
		} else {
			plus, minus = max(plus, -a), plus+a
			hasMinus = true
		}
	}
	if hasMinus {
		Println(max(plus, minus))
	} else {
		Println(plus)
	}
}