fixes

1-js/06-advanced-functions/01-recursion/01-sum-to/solution.md

@@ -37,4 +37,4 @@ P.S. Naturally, the formula is the fastest solution. It uses only 3 operations f
 
 The loop variant is the second in terms of speed. In both the recursive and the loop variant we sum the same numbers. But the recursion involves nested calls and execution stack management. That also takes resources, so it's slower.
 
-P.P.S. The standard describes a "tail call" optimization: if the recursive call is the very last one in the function (like in `sumTo` above), then the outer function will not need to resume the execution and we don't need to remember its execution context. In that case `sumTo(100000)` is countable. But if your JavaScript engine does not support it, there will be an error: maximum stack size exceeded, because there's usually a limitation on the total stack size.
+P.P.S. Some engines support the "tail call" optimization: if a recursive call is the very last one in the function (like in `sumTo` above), then the outer function will not need to resume the execution, so the engine doesn't need to remember its execution context. That removes the burden on memory, so counting `sumTo(100000)` becomes possible. But if the JavaScript engine does not support tail call optimization (most of them don't), there will be an error: maximum stack size exceeded, because there's usually a limitation on the total stack size.