var n,i,j,k,m:longint;
    a:array[1..800] of longint;
    
begin
  assign(input,'nrtri.in');
  assign(output,'nrtri.out');
  reset(input);
  rewrite(output);
  read(n);
  m:=0;
  for i:=1 to n do read(a[i]);
  for i:=1 to n-2 do
    for j:=i+1 to n-1 do
      for k:=j+1 to n do 
        if (a[i]+a[j]>=a[k]) and (a[i]+a[k]>=a[j]) and (a[j]+a[k]>=a[i]) then inc(m);
  write(m);
end.