day 6 simplify ivy solution and fix an off-by-n bug

day06/sol.ivy

@@ -11,13 +11,8 @@ op i loop a =
     (i+1) loop a
 
 op solve n =
-    i = ((1-n) drop iota rho input) o.+ (-1 + iota n)
+    i = iota n
-    1 loop input[i]
+    (i loop input)[-1]
-
-# if we were using rsc's @ patch then we could just do
-#   (unique@ input[i]) iota 1
-# instead of
-#   i loop input[i]
 
 solve 4
 solve 14