Count of Indices

Chef has given two lists, $A$ and $B$, each of which is a permutation of $N$. A permutation of $N$ is a list which contains all the numbers from $1$ to $N$ in some random order, and each number appears in the list once. He wants to find the number of indices such that if he were to swap the elements of the lists A to list B at same index, the two lists will still remain a permutation of $N$.