Var
     db:longint;
     i,j,a,b,c,k:word;
     n:word;
     et,v:array[-1..801] of 0..30000;
     f:text;
     kesz,jo:boolean;
Function szetvalogat(e,u:word):word;
var seged:integer;
begin
  seged:=et[e];
  while e<u do begin
    while (e<u) and (et[u]>=seged) do
      dec(u);
    if e<u then begin
      et[e]:=et[u];
      inc(e);
      while (e<u) and (et[e]<seged) do
        inc(e);
      et[u]:=et[e];
      dec(u);
    end;
  end;
  et[e]:=seged;
  szetvalogat:=e;
end;
procedure gyors(ah,fh:integer);
var k:integer;
begin
  if ah<fh then begin
    k:=szetvalogat(ah,fh);
    gyors(ah,k-1);
    gyors(k+1,fh);
  end;
end;
{function binker(e,u:integer):integer;
var k:integer;
begin
  if e>u then binker:=0
  else begin
    k:=(e+u) div 2;
    if (et[k]<=a+b) and then binker:=k
    else
      if mit<et[k] then binker:=binker(e,k-1,mit)
      else binker:=binker(k+1,u,mit);
  end;
end;               }
function binker(e,u:integer):integer;
var k:integer;
begin
    if e>u then binker:=0
    else begin
    k:=(e+u) div 2;
    c:=et[k];

    if e=u then begin
      if (a+b>=c)and(a+c>=b)and(b+c>=a) then binker:=e
      else binker:=0;
    end
    else

      if (a+b>=c)and(a+c>=b)and(b+c>=a) then begin
        if (a+b>=et[k-1])and(a+et[k-1]>=b)and(b+et[k-1]>=a) then binker:=binker(e,k-1)
        else binker:=k;
      end
      else binker:=binker(k+1,u);

    end;
end;

begin
Assign(f,'nrtri.in');
reset(f);
readln(f,n);
for i:=1 to n do
 read(f,et[i]);
close(f);
gyors(1,n);
db:=0;
i:=n;
while i>2 do begin
  a:=et[i];
  j:=i-1;
  while j>1 do begin
    b:=et[j];
    k:=binker(1,j-1);
    if k<>0 then db:=db+(j-k);
    j:=j-1;
  end;
i:=i-1;
end;
assign(f,'nrtri.out');
rewrite(f);
writeln(f,db);
close(f)
end.