Program triunghiuri;

var V : array [1..900] of longint;
    b1,b2 :array[0..1 shl 17 ] of char;
    n,i,l,j,m : longint;

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

procedure qsort(left,right:longint);
      var i,j,pivot:longint;
       begin
        i:=left; j:=right; pivot:=V[((right+left) div 2)];
         repeat
          while V[i]<pivot do inc(i);
          while V[j]>pivot do dec(j);
           if i<=j then begin
                         swap(V[i],V[j]);
                         inc(i);
                         dec(j);
                        end;

         until i>j;
        if i<right then qsort(i,right);
        if j>left then qsort(left,j);
       end;
begin
  assign(input,'nrtri.in'); settextbuf(input,b1); reset(input);
  assign(output,'nrtri.out'); settextbuf(output,b2); rewrite(output);
  readln(n); l:=0;
  for i:=1 to n do read(V[i]);
  qsort(1,n);
  for i:=1 to n-2 do
      for j:=i+1 to n-1 do begin
                                 m:=j+1;
                                 while (V[m]<=(V[i]+V[j])) and (m<=n) do
                              begin
                                   l:=l+1;
                                   m:=m+1;
                               end;
                           end;

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