import java.io.*;
import java.util.*;
import java.util.function.*;
import java.util.stream.*;

public class Main {
    static int[] values;
    static long[][] dp;
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        values = new int[n];
        for (int i = 0; i < n; i++) {
            values[n - i - 1] = sc.nextInt();
        }
        dp = new long[n][2];
        for (long[] arr : dp) {
            Arrays.fill(arr, -1);
        }
        long ans = Long.MIN_VALUE;
        for (int i = 0; i < n; i++) {
            ans = Math.max(ans, dfw(i - 1, 0) - values[i]);
        }
        System.out.println(ans);
    }
    
    static long dfw(int idx, int v) {
        if (idx < 0) {
            return 0;
        }
        if (dp[idx][v] < 0) {
            dp[idx][v] = Math.max(dfw(idx - 1, v), dfw(idx - 1, v ^ 1) + values[idx] * (v == 0 ? 1 : -1));
        }
        return dp[idx][v];
    }
}

class Scanner {
    BufferedReader br;
    StringTokenizer st = new StringTokenizer("");

    public Scanner() {
        try {
            br = new BufferedReader(new InputStreamReader(System.in));
        } catch (Exception e) {
            
        }
    }
    
    public int nextInt() {
        return Integer.parseInt(next());
    }
    
    public long nextLong() {
        return Long.parseLong(next());
    }
    
    public double nextDouble() {
        return Double.parseDouble(next());
    }
    
    public String next() {
        try {
            while (!st.hasMoreTokens()) {
                st = new StringTokenizer(br.readLine());
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            return st.nextToken();
        }
    }
    
}