var a:array[1..800] of word; n,i,j,k,x:word; fi,fo:text;
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-2 do
                for j:=i+1 to n-1 do
                        for k:=j+1 to n do
                            if (a[i]+a[j]>=a[k]) and (a[j]+a[k]>=a[i]) and (a[k]+a[i]>=a[j]) then inc(x);
      writeln(fo,x);
      close(Fi); close(Fo);
end.