Okay, so I did some testing, and then I noticed that you're not storing already computed answer. If you don't use answer till now, then you're basically doing greedy, and not dp. Your function $$$solve(idx,used)$$$ just calculates maximum OR possible using at most $$$"used"$$$ multiplications and indices upto $$$"idx"$$$, but if your answer from indices $$$"idx+1", ... n$$$ has some bits already, then instead of maximizing $$$OR$$$ from left side ( $$$0,...idx$$$ ) you instead want maximum and trying to exclude those set bits already.

Basically, you need $$$prev$$$ ( already calculated answer ) as a state too.

Changed your code only a little bit ( used map to memoize, since we need to store long long ) here, but it gives TLE because now there are too many states. I guess you could solve it iteratively instead of using recursion.