using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using System.Runtime.CompilerServices;
using System.Text;
using System.Diagnostics;
using System.Numerics;
using static System.Console;
using static System.Convert;
using static System.Math;
using static Template;
using Pi = Pair<int, int>;

class Solver
{
    public void Solve(Scanner sc)
    {
        var N = sc.Int;
        var seg = new LazySegmentTree<long, long>(N, int.MinValue, 0, Max, (a, b) => a + b, (a, b) => a + b);
        for (int i = 0; i < N; i++)
        {
            seg[i] = 0;
        }
        var res=0L;
        seg.Build();
        for (int i = 0; i < N; i++)
        {
            long x, s;
            sc.Make(out x, out s);
            var max = seg.Query(0, i);
            chmax(ref res, max + s - x);
            chmax(ref res, s);
            seg.Update(i, i + 1, x + s);
            seg.Update(0, i, s);
        }
        Console.WriteLine(res);
    }
}

public class LazySegmentTree<T, E>
{
    protected readonly int size;
    protected readonly T idT;
    protected readonly T[] data;
    protected readonly E idE;
    protected readonly E[] lazy;
    protected readonly Func<T, T, T> mergeT;
    protected readonly Func<T, E, T> update;
    protected readonly Func<E, E, E> mergeE;
    protected readonly Func<E, int, E> sec;
    protected readonly Comparison<E> cmpE;

    public T this[int i]
    {
        get { return data[i + size - 1]; }
        set { data[i + size - 1] = value; }
    }
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    protected int Parent(int index)
        => (index - 1) >> 1;
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    protected int Left(int index)
        => (index << 1) + 1;
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    protected int Right(int index)
        => (index + 1) << 1;
    public LazySegmentTree(int N, T idT, E idE, Func<T, T, T> mergeT, Func<T, E, T> update = null, Func<E, E, E> mergeE = null, Func<E, int, E> sec = null, Comparison<E> cmp = null)
    {
        this.mergeT = mergeT;
        this.size = 1;
        this.idT = idT;
        this.idE = idE;
        this.update = update ?? ((a, b) => a);
        this.mergeE = mergeE ?? ((a, b) => b);
        this.sec = sec ?? ((a, b) => a);
        cmpE = cmp ?? Comparer<E>.Default.Compare;
        while (this.size < N)
            this.size <<= 1;
        data = new T[2 * this.size - 1];
        for (var i = 0; i < 2 * this.size - 1; i++)
            data[i] = idT;
        lazy = Enumerable.Repeat(0, 2 * this.size + 1).Select(_ => idE).ToArray();
    }
    protected void eval(int len, int k)
    {
        if (cmpE(lazy[k], idE) == 0) return;
        if (Right(k) < size * 2)
        {
            lazy[Left(k)] = mergeE(lazy[Left(k)], lazy[k]);
            lazy[Right(k)] = mergeE(lazy[Right(k)], lazy[k]);
        }
        data[k] = update(data[k], sec(lazy[k], len));
        lazy[k] = idE;
    }
    public void Build()
    {
        for (int i = size - 2; i >= 0; i--)
            data[i] = mergeT(data[Left(i)], data[Right(i)]);
    }
    public void Update(int left, int right, E value, int k = 0, int l = 0, int r = -1)
    {
        if (r == -1) r = size;
        eval(r - l, k);
        if (r <= left || right <= l) return;
        if (left <= l && r <= right)
        {
            lazy[k] = mergeE(lazy[k], value);
            eval(r - l, k);
        }
        else
        {
            Update(left, right, value, Left(k), l, (l + r) >> 1);
            Update(left, right, value, Right(k), (l + r) >> 1, r);
            data[k] = mergeT(data[Left(k)], data[Right(k)]);
        }
    }
    public T Query(int left, int right, int k = 0, int l = 0, int r = -1)
    {
        if (r == -1) r = size;
        if (r <= left || right <= l) return idT;
        eval(r - l, k);
        if (left <= l && r <= right) return data[k];
        else
            return mergeT(Query(left, right, Left(k), l, (l + r) >> 1), Query(left, right, Right(k), (l + r) >> 1, r));
    }

    public int Find(int st, Func<T, bool> check)
    {
        var x = idT;
        return Find(st, check, ref x, 0, 0, size);
    }
    private int Find(int st, Func<T, bool> check, ref T x, int k, int l, int r)
    {
        if (l + 1 == r)
        { x = mergeT(x, data[k]); return check(x) ? k - size + 1 : -1; }
        eval(r - l, k);
        var m = (l + r) >> 1;
        if (m <= st) return Find(st, check, ref x, Right(k), m, r);
        if (st <= l && !check(mergeT(x, data[k])))
        { x = mergeT(x, data[k]); return -1; }
        var xl = Find(st, check, ref x, Left(k), l, m);
        if (xl >= 0) return xl;
        return Find(st, check, ref x, Right(k), m, r);
    }
}

#region Template
public static class Template
{
    static void Main(string[] args)
    {
        Console.SetOut(new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false });
        new Solver().Solve(new Scanner());
        Console.Out.Flush();
    }
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static bool chmin<T>(ref T a, T b) where T : IComparable<T> { if (a.CompareTo(b) > 0) { a = b; return true; } return false; }
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static bool chmax<T>(ref T a, T b) where T : IComparable<T> { if (a.CompareTo(b) < 0) { a = b; return true; } return false; }
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static void swap<T>(ref T a, ref T b) { var t = b; b = a; a = t; }
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static void swap<T>(this IList<T> A, int i, int j) { var t = A[i]; A[i] = A[j]; A[j] = t; }
    public static T[] Create<T>(int n, Func<T> f) { var rt = new T[n]; for (var i = 0; i < rt.Length; ++i) rt[i] = f(); return rt; }
    public static T[] Create<T>(int n, Func<int, T> f) { var rt = new T[n]; for (var i = 0; i < rt.Length; ++i) rt[i] = f(i); return rt; }
    public static IEnumerable<T> Shuffle<T>(this IEnumerable<T> A) => A.OrderBy(v => Guid.NewGuid());
    public static int CompareTo<T>(this T[] A, T[] B, Comparison<T> cmp = null) { cmp = cmp ?? Comparer<T>.Default.Compare; for (var i = 0; i < Min(A.Length, B.Length); i++) { int c = cmp(A[i], B[i]); if (c > 0) return 1; else if (c < 0) return -1; } if (A.Length == B.Length) return 0; if (A.Length > B.Length) return 1; else return -1; }
    public static int MaxElement<T>(this IList<T> A, Comparison<T> cmp = null) { cmp = cmp ?? Comparer<T>.Default.Compare; T max = A[0]; int rt = 0; for (int i = 1; i < A.Count; i++) if (cmp(max, A[i]) < 0) { max = A[i]; rt = i; } return rt; }
    public static T PopBack<T>(this List<T> A) { var v = A[A.Count - 1]; A.RemoveAt(A.Count - 1); return v; }
    public static void Fail<T>(T s) { Console.WriteLine(s); Console.Out.Close(); Environment.Exit(0); }
}
public class Scanner
{
    public string Str => Console.ReadLine().Trim();
    public int Int => int.Parse(Str);
    public long Long => long.Parse(Str);
    public double Double => double.Parse(Str);
    public int[] ArrInt => Str.Split(' ').Select(int.Parse).ToArray();
    public long[] ArrLong => Str.Split(' ').Select(long.Parse).ToArray();
    public char[][] Grid(int n) => Create(n, () => Str.ToCharArray());
    public int[] ArrInt1D(int n) => Create(n, () => Int);
    public long[] ArrLong1D(int n) => Create(n, () => Long);
    public int[][] ArrInt2D(int n) => Create(n, () => ArrInt);
    public long[][] ArrLong2D(int n) => Create(n, () => ArrLong);
    private Queue<string> q = new Queue<string>();
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public T Next<T>() { if (q.Count == 0) foreach (var item in Str.Split(' ')) q.Enqueue(item); return (T)Convert.ChangeType(q.Dequeue(), typeof(T)); }
    public void Make<T1>(out T1 v1) => v1 = Next<T1>();
    public void Make<T1, T2>(out T1 v1, out T2 v2) { v1 = Next<T1>(); v2 = Next<T2>(); }
    public void Make<T1, T2, T3>(out T1 v1, out T2 v2, out T3 v3) { Make(out v1, out v2); v3 = Next<T3>(); }
    public void Make<T1, T2, T3, T4>(out T1 v1, out T2 v2, out T3 v3, out T4 v4) { Make(out v1, out v2, out v3); v4 = Next<T4>(); }
    public void Make<T1, T2, T3, T4, T5>(out T1 v1, out T2 v2, out T3 v3, out T4 v4, out T5 v5) { Make(out v1, out v2, out v3, out v4); v5 = Next<T5>(); }
    public void Make<T1, T2, T3, T4, T5, T6>(out T1 v1, out T2 v2, out T3 v3, out T4 v4, out T5 v5, out T6 v6) { Make(out v1, out v2, out v3, out v4, out v5); v6 = Next<T6>(); }
    public void Make<T1, T2, T3, T4, T5, T6, T7>(out T1 v1, out T2 v2, out T3 v3, out T4 v4, out T5 v5, out T6 v6, out T7 v7) { Make(out v1, out v2, out v3, out v4, out v5, out v6); v7 = Next<T7>(); }
    //public (T1, T2) Make<T1, T2>() { Make(out T1 v1, out T2 v2); return (v1, v2); }
    //public (T1, T2, T3) Make<T1, T2, T3>() { Make(out T1 v1, out T2 v2, out T3 v3); return (v1, v2, v3); }
    //public (T1, T2, T3, T4) Make<T1, T2, T3, T4>() { Make(out T1 v1, out T2 v2, out T3 v3, out T4 v4); return (v1, v2, v3, v4); }
}
public class Pair<T1, T2> : IComparable<Pair<T1, T2>>
{
    public T1 v1;
    public T2 v2;
    public Pair() { }
    public Pair(T1 v1, T2 v2)
    { this.v1 = v1; this.v2 = v2; }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public int CompareTo(Pair<T1, T2> p)
    {
        var c = Comparer<T1>.Default.Compare(v1, p.v1);
        if (c == 0)
            c = Comparer<T2>.Default.Compare(v2, p.v2);
        return c;
    }
    public override string ToString() => $"{v1.ToString()} {v2.ToString()}";
    public void Deconstruct(out T1 a, out T2 b) { a = v1; b = v2; }
}

public class Pair<T1, T2, T3> : Pair<T1, T2>, IComparable<Pair<T1, T2, T3>>
{
    public T3 v3;
    public Pair() : base() { }
    public Pair(T1 v1, T2 v2, T3 v3) : base(v1, v2)
    { this.v3 = v3; }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public int CompareTo(Pair<T1, T2, T3> p)
    {
        var c = base.CompareTo(p);
        if (c == 0)
            c = Comparer<T3>.Default.Compare(v3, p.v3);
        return c;
    }
    public override string ToString() => $"{base.ToString()} {v3.ToString()}";
    public void Deconstruct(out T1 a, out T2 b, out T3 c) { Deconstruct(out a, out b); c = v3; }
}
#endregion


Measured memory_bytes: 30992