var v:array[1..800] of integer;
    f,g:text;
    i,j,k,aux,p,n:integer;
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]);
for i:=1 to n-1 do
    for j:=i+1 to n do
       if v[i]>v[j] then
           begin
            aux:=v[i];
            v[i]:=v[j];
            v[j]:=aux;
           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[k]<=v[i]+v[j] then
                  p:=p+1;
write(g,p);
close(f);
close(g);
end.