program p1;
var a,b:array[0..801] of integer;
    f,g:text;
    i,n,j,k,u,aux,sol:longint;
procedure Sort(l, r: Integer);
var
  i, j, x, y: integer;
begin
  i := l; j := r; x := a[(l+r) DIV 2];
  repeat
    while a[i] < x do i := i + 1;
    while x < a[j] do j := j - 1;
    if i <= j then
    begin
      y := a[i]; a[i] := a[j]; a[j] := y;
      i := i + 1; j := j - 1;
    end;
  until i > j;
  if l < j then Sort(l, j);
  if i < r then Sort(i, r);
end;

begin
assign(f,'nrtri.in');reset(F);
assign(g,'nrtri.out');rewrite(G);
readln(f,n);
for i:=1 to n do begin
                read(f,a[i]);
                 end;
sort(1,n);
for i:=1 to n do
         for j:=i+1 to n do
                for k:=j+1 to n do
                        if a[i]+a[j]>=a[k] then inc(sol);
writeln(g,sol);
close(F);
close(G);
end.