program pdas1;
var a:array[0..801] of integer;
    f,g:text;
    i,n,j,k,u,aux,sol,poz,t:longint;
    b1,b2:array[0..1 shl 17 ] of char;
    p1:boolean;
procedure Sort(l, r: Integer);
var
  i, j, x, y: integer;
begin
  i := l; j := r; x := a[(l+r) DIV 2];
  repeat
    while a[i] < x do i := i + 1;
    while x < a[j] do j := j - 1;
    if i <= j then
    begin
      y := a[i]; a[i] := a[j]; a[j] := y;
      i := i + 1; j := j - 1;
    end;
  until i > j;
  if l < j then Sort(l, j);
  if i < r then Sort(i, r);
end;
{procedure cauta (i,j:integer; x:longint);
var mijl:integer;
begin
if i<=j then begin
        mijl:=(i+j) div 2;
        if a[mijl]>=x then begin
                        poz:=mijl;
                        p1:=true;
                           end
        else
        if a[mijl]<x then cauta(i,mijl-1,x);
           end;
end;          }
begin
assign(f,'nrtri.in');settextbuf(g,b1);reset(F);
assign(g,'nrtri.out');settextbuf(g,b2);rewrite(G);
readln(f,n);
for i:=1 to n do
                read(f,a[i]);
sort(1,n);
for t:=1 to n-2 do
        for k:=t+1 to n-1 do
                for i:=k+1 to  n do
                        if a[t]+a[k]>=a[i] then inc(sol)
                                else break;
writeln(g,sol);
close(F);
close(G);
end.