Program triunghiuri;

var V : array [1..900] of longint;
    n,i,l,j,k : longint;

procedure swap ( var x,y : longint);
   var aux : longint;
     begin
       aux:=x;
       x:=y;
       y:=aux;

     end;

begin
  assign(input,'nrtri.in'); reset(input);
  assign(output,'nrtri.out'); rewrite(output);
  readln(n); l:=0;
  for i:=1 to n do read(V[i]);
   for i:=1 to n-2 do
      for j:=i+1 to n-1 do
        for k:=j+1 to n do
           if (V[k]<=V[j]+V[i]) and (V[k]>=V[j]-V[i])
             then l:=l+1;

  writeln(l);


  close(input); close(output);
end.