var a:array[1..800] of longint;
    f,g:text;
    i,j,h,k,n,aux:longint;
begin
assign(f,'nrtri.in');reset(f);
assign(g,'nrtri.out');rewrite(g);
readln(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;

k:=0;

for i:=1 to n-2 do
for j:=i+1 to n-1 do
begin
 h:=j+1;
 while h<=n do
 if a[i]+a[j]>=a[h] then begin inc(k); h:=h+1; end
                    else break;
end;
write(g,k);
close(f);
close(g);
end.