var
	fi,fo:text;
  a:array[1..800]of byte;
  i,j,k,nr,n:word;
begin
	assign(fi,'nrtri.in');reset(fi);
  assign(fo,'nrtri.out');rewrite(fo);
  readln(fi,n);
  for i:= 1 to n do
  	read(fi,a[i]);
  for i:= 1 to n do
  	for j:= (i+1) to n do
    	begin
        for k:= j+1 to n do
        	if a[i]+a[j]>=a[k] then
          	if a[i]+a[k]>=a[j] then
            	if a[j]+a[k]>=a[i] then
              	inc(nr);
      end;
  writeln(fo,nr);
  close(fo);
end.