var n,i,j,u,m:longint;
    a,v:array[-1..800] of longint;

begin
  assign(input,'nrtri.in');
  assign(output,'nrtri.out');
  reset(input);
  rewrite(output);

  read(n);
  for i:=1 to n do
    read(a[i]);
  m:=0;
  for i:=1 to n-2 do
    for j:=i+1 to n-1 do
      for u:=j+1 to n do begin
        if (a[i]+a[j]>=a[u])
          and (a[j]+a[u]>=a[i])
          and (a[i]+a[u]>=a[j])
            then
            inc(m);
      end;
  write(m);
end.