Fix missing tag close

lectures/java_rep/index.html

@@ -282,7 +282,7 @@ <h2>Objects and pointers</h2>
 been a little mysterious. However, the representation of pointers is quite
 straightforward: a pointer is represented just like the (unsigned) number that is
 the memory address of the memory location it points to. Since modern computers
-have addresses up to 2<sup>64</sup-1, the representation of a pointer takes up
+have addresses up to 2<sup>64</sup>-1, the representation of a pointer takes up
 64 bits, or two 32-bit words.
 </p>