/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
int ans;
bool fun(TreeNode* t1,TreeNode* t2){
    if(!t1)
        return t2 == nullptr;
    if(!t2)
        return false;
    if(t1->val == t2->val){
        bool flg = fun(t1->left,t2->left) and fun(t1->right,t2->right);
        if(!flg){
            ans++;
            return fun(t1->left,t2->right) and fun(t1->right,t2->left);
        }else return true;
    }else
        return false;
}
int Solution::solve(TreeNode* A, TreeNode* B) {
    ans = 0;
    if(fun(A,B))
        return ans;
    return -1;
}