Palindrome Flipping

Chef has a binary string $S$ of length $N$. In one operation, Chef can: - Select two indices $i$ and $j$ $(1 \le i, j \le N, i \ne j)$ and flip $S_i$ and $S_j$. (i.e. change $0$ to $1$ and $1$ to $0$) For example, if $S = 10010$ and chef applys operation on $i = 1$ and $j = 3$ then: $\underline{1}0\underline{0}10 \rightarrow 00110$. Find if it is possible to convert $S$ to a palindrome by appl