program nrt;
var f:text;
    i,j,k,n,nr:longint;
    a:array[1..800] of longint;
begin
  assign(f,'nrtri.in');
  reset(f);
  readln(f,n);
  for i:=1 to n do read(f,a[i]);
  close(f);
  assign(f,'nrtri.out');
  rewrite(f);
  nr:=0;
  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]>=abs(a[j]-a[k]))and(a[j]+a[k]>=a[i]) then nr:=nr+1;
  writeln(f,nr);
  close(f);
end.