Program triunghiuri;
var V : array [1..900] of longint;
    n,i,l,j,k : longint;

begin
  assign(input,'nrtri.in'); reset(input);
  assign(output,'nrtri.out'); rewrite(output);
  readln(n);
  for i:=1 to n do read(V[i]);
   for i:=1 to n-2 do
      for j:=i+1 to n-1 do
        for k:=j+1 to n do
           if (V[i]+V[j]>=V[k]) and (V[i]+V[k]>=V[j]) and (V[j]+V[k]>=V[i])
             then l:=l+1;

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