using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;
using System.Globalization;
using System.Runtime.CompilerServices;
using System.Runtime.Intrinsics.X86;
using System.Runtime.Intrinsics.Arm;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var n = NN;
        var a = NList;
        var tmp = 0L;
        for (var i = 0; i < n; ++i) tmp += a[i * 2] - a[i * 2 + 1];
        var ans = tmp;
        for (var i = n - 1; i >= 0; --i)
        {
            tmp -= a[i * 2] - a[i * 2 + 1];
            tmp -= a[i * 2] - a[i * 2 + 1];
            ans = Math.Max(ans, tmp);
        }
        WriteLine(ans);
        
    }
}