const NMAX=30002;
var n,i,j,k:longint;
    v:array[0..801] of longint;
    f,g:text;
    sol:int64;
begin
 assign(f,'nrtri.in');reset(f);
 assign(g,'nrtri.out');rewrite(g);
 readln(f,n);
 for i:=1 to n do
  read(f,v[i]);
 sol:=0;
 for i:=1 to n do
  for j:=i+1 to n do
   if (v[i]>v[j]) then
    begin
    k:=v[i];
    v[i]:=v[j];
    v[j]:=k;
    end;
 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])  then
     sol:=sol+1;
 write(g,sol);
 close(f);close(g);
end.