using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Linq;
using System.Numerics;

namespace AtCoderWorkspace
{
    public class Solver
    {
        public void Solve()
        {
            var cin = new Scanner();
            var n = cin.nextInt();
            var arr = cin.ArrayLong(n);

            Array.Sort(arr);

            var ans = 0;
            for (int i = 0; i < n; i++)
            {
                for (int j = i+1; j < n; j++)
                {
                    if (i == j) continue;

                    var ab = arr[i] + arr[j];
                    var bs = new BinarySearch<long>(arr, (mid) =>
                    {
                        return mid < ab;
                    });

                    ans += bs.Search() - j;
                }
            }            
            Console.WriteLine(ans);
        }
    }

    class BinarySearch<T>
    {
        T[] a;
        Func<T, bool> isOK;

        /// <param name="a">探索する配列</param>
        /// <param name="isOK">midの判定</param>
        public BinarySearch(T[] a, Func<T, bool> isOK)
        {
            this.a = a;
            this.isOK = isOK;
        }

        public int Search()
        {
            int ok = -1;
            int ng = a.Length;

            while (Math.Abs(ok - ng) > 1)
            {
                int mid = (ok + ng) / 2;

                if (isOK(a[mid])) ok = mid;
                else ng = mid;
            }
            return ok;
        }
    }

    class Scanner
    {
        string[] s;
        int i;

        char[] cs = new char[] { ' ' };

        public Scanner()
        {
            s = new string[0];
            i = 0;
        }

        public string next()
        {
            if (i < s.Length) return s[i++];
            string st = Console.ReadLine();
            while (st == "") st = Console.ReadLine();
            s = st.Split(cs, StringSplitOptions.RemoveEmptyEntries);
            if (s.Length == 0) return next();
            i = 0;
            return s[i++];
        }

        public int nextInt()
        {
            return int.Parse(next());
        }
        public int[] ArrayInt(int N, int add = 0)
        {
            int[] Array = new int[N];
            for (int i = 0; i < N; i++)
            {
                Array[i] = nextInt() + add;
            }
            return Array;
        }

        public int[] DPArrayInt(int N, int ex)
        {
            int[] Array = new int[N + ex];
            for (int i = 0; i < N; i++)
            {
                Array[i] = nextInt();
            }
            return Array;
        }

        public long nextLong()
        {
            return long.Parse(next());
        }

        public long[] ArrayLong(int N, long add = 0)
        {
            long[] Array = new long[N];
            for (int i = 0; i < N; i++)
            {
                Array[i] = nextLong() + add;
            }
            return Array;
        }

        public long[] DPArrayLong(int N, int ex)
        {
            long[] Array = new long[N + ex];
            for (int i = 0; i < N; i++)
            {
                Array[i] = nextLong();
            }
            return Array;
        }

        public double nextDouble()
        {
            return double.Parse(next());
        }


        public double[] ArrayDouble(int N, double add = 0)
        {
            double[] Array = new double[N];
            for (int i = 0; i < N; i++)
            {
                Array[i] = nextDouble() + add;
            }
            return Array;
        }
    }

    class Program
    {
        static void Main(string[] s) => new Solver().Solve();
    }
}


Measured memory_bytes: 19628