var t:array[1..800]of integer;
    n,m,i,j,k:longint;
begin
 assign(input,'nrtri.in');
 reset(input);
  readln(n);
  for i:=1 to n do read(t[i]);
 close(input);

  m:=0;
  for i:=1 to n-2 do
   for j:=i+1 to n-1 do
    for k:=j+1 to n do
     if (t[i]+t[j]>=t[k])and(t[k]+t[j]>=t[i])and(t[i]+t[k]>=t[j]) then m:=m+1;

 assign(output,'nrtri.out');
 rewrite(output);
  write(m);
 close(output);
end.