#include <cstdio>
#include <iostream>
#include <vector>
#include <unordered_map>
#include <algorithm>
using namespace std;

class TreeNode {
public:
    TreeNode(int v) :data(v), left(NULL), right(NULL) { }

    int data;
    TreeNode *left;
    TreeNode *right;
};

class BinarySearchTree {
public:
    BinarySearchTree(int n) {
        this->nodeNum = n;
    }

    void build(const vector<int> &preOrd, const vector<int> &inOrd) {
        this->root = this->internalBuild(preOrd, inOrd, 0, preOrd.size() - 1, 0, inOrd.size() - 1);
    }

    bool isIn(int v) {
        return this->valToTreeNode.find(v) != this->valToTreeNode.end();
    }

    int findLCA(int u, int v) {
        TreeNode *t = this->root;
        while (t) {
            if (t->data > v) t = t->left;
            else if (t->data < u) t = t->right;
            else return t->data;
        }
        return -1;
    }

private:
    // build binary tree from pre order and in order
    TreeNode* internalBuild(const vector<int> &preOrd, const vector<int> &inOrd, 
        int preLeft, int preRight, int inLeft, int inRight) {
        TreeNode *node = new TreeNode(preOrd[preLeft]);
        int inRootPos;
        for (inRootPos = inLeft; inRootPos <= inRight; inRootPos++)
            if (inOrd[inRootPos] == node->data) break;
        int leftSize = inRootPos - inLeft;
        int rightSize = inRight - inRootPos;
        if (leftSize > 0)
            node->left = this->internalBuild(preOrd, inOrd, preLeft + 1, preLeft + leftSize, inLeft, inRootPos - 1);
        if (rightSize > 0)
            node->right = this->internalBuild(preOrd, inOrd, preLeft + leftSize + 1, preRight, inRootPos + 1, inRight);
        this->valToTreeNode[node->data] = node;
        return node;
    }

private:
    int nodeNum;
    TreeNode * root;
    unordered_map<int, TreeNode*> valToTreeNode; // map value to tree node pointer
};

int main() {
    int m, n, u, v;
    cin >> m >> n;
    BinarySearchTree bst(n);
    vector<int> preOrd(n), inOrd(n);
    for (int i = 0; i < n; i++) {
        cin >> preOrd[i];
        inOrd[i] = preOrd[i]; // inOrd doesn't mean elements from 1 to n like example, that sucks.
    }
    sort(inOrd.begin(), inOrd.end());
    bst.build(preOrd, inOrd);
    
    for (int i = 0; i < m; i++) {
        cin >> u >> v;
        if (!bst.isIn(u) || !bst.isIn(v)) {
            bool t = !bst.isIn(u) && !bst.isIn(v);
            cout << "ERROR: ";
            if (!bst.isIn(u)) cout << u << " ";
            if (t) cout << "and ";
            if (!bst.isIn(v)) cout << v << " ";
            cout << (t ? "are" : "is") << " not found." << endl;
        } else {
            int lca = bst.findLCA(u > v ? v : u, u > v ? u : v);
            if (lca != u && lca != v) {
                cout << "LCA of " << u << " and " << v << " is " << lca << "." << endl;
            } else {
                cout << (lca == u ? u : v) << " is an ancestor of " << (u + v - lca) << "." << endl;
            }
        }
    }
    return 0;
}