import core.bitop;
import std.algorithm;
import std.ascii;
import std.bigint;
import std.conv;
import std.functional;
import std.math;
import std.numeric;
import std.range;
import std.stdio;
import std.string;
import std.random;
import std.typecons;
import std.container;

enum MAX = 1_000_100;
ulong MOD = 1_000_000_007;
ulong INF = 1_000_000_000_000;
alias sread = () => readln.chomp();
alias Pair = Tuple!(long, "cost", long, "num");
alias PQueue(T, alias less = "a<b") = BinaryHeap!(Array!T, less);

void main()
{
    auto n = lread();
    auto l = aryread();
    l.sort();
    long ans;
    foreach (i; iota(n))
    {
        foreach (j; iota(i + 1, n))
        {
            auto minidx = max(l.upper_bound(l[j] - l[i]), j);
            auto maxidx = l.lower_bound(l[j] + l[i]);
            if(maxidx != j)
                ans += maxidx - minidx;
    }
}
ans.writeln();
}

// limitより小さい限界のインデックス
auto lower_bound(T)(T[] ary, T limit)
{
    long ok = -1, ng = ary.length;
    while (abs(ng - ok) > 1)
    {
        auto mid = (ok + ng) / 2;
        if (ary[mid] >= limit)
            ng = mid;
        else
            ok = mid;
    }
    return ok;
}

// limitより大きい最小のインデックス
auto upper_bound(T)(T[] ary, T limit)
{
    long ok = ary.length, ng = -1;
    while (abs(ok - ng) > 1)
    {
        auto mid = (ok + ng) / 2;
        if (ary[mid] > limit)
            ok = mid;
        else
            ng = mid;
    }
    return ok;
}

T lread(T = long)()
{
    return readln.chomp.to!T();
}

T[] aryread(T = long)()
{
    return readln.split.to!(T[])();
}

void scan(TList...)(ref TList Args)
{
    auto line = readln.split();
    foreach (i, T; TList)
    {
        T val = line[i].to!(T);
        Args[i] = val;
    }
}
