var nt,n,i,j,k,nr:longint;
    a:array[1..800] of integer;
    f1,f2:text;
begin
assign(f1,'nrtri.in');
assign(f2,'nrtri.out');
reset(f1);
rewrite(f2);
readln(f1,n);
for i:=1 to n do
 read(f1,a[i]);
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]) and
      (a[i]+a[k]>=a[j]) and
      (a[j]+a[k]>=a[i]) then nt:=nt+1;
writeln(f2,nt);
close(f1);
close(f2);
end.