#![allow(unused_imports)]

fn main() {
    input! {
        n: usize,
        a: [i64; n],
    }
    let mut dp = mvec![None; (n+1, 2)];
    dp[0][0] = Some(0);
    for i in 0..n {
        for j in 0..2 {
            if let Some(v) = dp[i][j] {
                chmax!(dp[i + 1][j], Some(v));
                chmax!(
                    dp[i + 1][j ^ 1],
                    Some(v + a[i] * if j == 0 { -1 } else { 1 })
                );
            }
        }
    }
    println!("{}", dp[n][0].max(dp[n][1]).unwrap());
}

use proconio::{input, marker::*};
use std::{cmp::Reverse, collections::*};

#[macro_export]
macro_rules! chmax {
    ($a:expr, $b:expr) => {{
        let tmp = $b;
        if $a < tmp {
            $a = tmp;
            true
        } else {
            false
        }
    }};
}

#[macro_export]
macro_rules! chmin {
    ($a:expr, $b:expr) => {{
        let tmp = $b;
        if $a > tmp {
            $a = tmp;
            true
        } else {
            false
        }
    }};
}

#[macro_export]
/// mvec![]
macro_rules! mvec {
    ($val:expr; ()) => {
        $val
    };
    ($val:expr; ($size:expr $(,$rest:expr)*)) => {
        vec![mvec![$val; ($($rest),*)]; $size]
    };
}