var i,j,k,l,m,n:longint; f1,f2:text; a:array[1..800] of integer;
begin
assign(f1,'nrtri.in');
reset(f1);
assign(f2,'nrtri.out');
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 l:=j+1 to n do
if (a[i]+a[j]>=a[l]) and (a[j]+a[l]>=a[i]) and (a[i]+a[l]>=a[j]) then Inc(k);
writeln(f2,k);
close(f1);
close(f2);

end.