var a:array[1..800]of longint;
i,j,k,n:integer;
s,aux:longint;
f,g:text;
begin
assign(f,'nrtri.in');reset(f);
assign(g,'nrtri.out');rewrite(g);
read(f,n);
for i:=1 to n do
read(f,a[i]);
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;
for i:=1 to n-2 do
for j:=i+1 to n-1 do
if a[i]+a[j]>=a[j+1] then s:=s+1
else break;
write(g,s);
close(f);
close(g);
end.