Binary Minimal

Alice is given a binary string $S$ of length $N$. She can perform the following operations on string $S$: - Select an index $1\le i\le |S|$ and delete the character $S_i$.; - Select an index $1\le i\le |S|$ and flip the character $S_i$. Note that while flipping $1$ becomes $0$ and vice-versa. Find the **lexicographically smallest** string Alice can obtain using **at most** $K$ operations. Note