fn main() {
	input!{
		n: usize,
		a: [i64; n],
	}

	// dp[i個選択][(偶数個、奇数個)選んだ状態j] = 総和のmax
	let mut dp = vec![vec![-INF; 2]; n+1];
	dp[0][0] = 0;

	for i in 1..=n {
		// 遷移後が0のときは、a[i]
		dp[i][0] = max(dp[i-1][0], dp[i-1][1] + a[i-1]);

		// 遷移後が1のときは、a[i]*(-1)
		dp[i][1] = max(dp[i-1][1], dp[i-1][0] - a[i-1]);
	}
	println!("{}", max(dp[n][0], dp[n][1]));
}

// const MOD17: usize = 1000000007;
// const MOD93: usize = 998244353;
const INF: i64 = 1 << 60;
// let dx = vec![!0, 0, 1, 0]; // 上左下右
// let dy = vec![0, !0, 0, 1]; // 上左下右
// let d = vec!{(!0, 0), (0, !0), (1, 0), (0, 1)}; // 上左下右

#[allow(unused)]
use proconio::{input, marker::Chars, marker::Usize1};

#[allow(unused)]
use std::{
	mem::swap,
	cmp::min, cmp::max,
	cmp::Reverse,
	collections::HashSet, collections::BTreeSet,
	collections::HashMap, collections::BTreeMap,
	collections::BinaryHeap,
	collections::VecDeque,
	iter::FromIterator,
};