var f,g:text;
    n,i,nr:integer;
a:array[1..800] of integer;

procedure citire;
begin
assign(f,'nrtri.in');reset(f);
readln(f,n);
for i:=1 to n do
    read(f,a[i]);
close(f);
end;

procedure sort;
var aux,j:integer;
begin
for i:=1 to n-1 do
for j:=i+1 to n do
if a[i]>a[j] then begin
        aux:=a[i];
        a[i]:=a[j];
        a[j]:=aux
        end
end;

procedure fa;
var i,j,k:integer;
begin
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]+a[j]>=a[k]) then inc(nr)
                             else break;

assign(g,'nrtri.out'); rewrite(g);
write(g,nr);
close(g)
end;

begin
citire;
sort;
fa;
end.