#include <bits/stdc++.h>

using namespace std;

string ltrim(const string &);
string rtrim(const string &);
vector<string> split(const string &);

/*
 * Complete the 'queensAttack' function below.
 *
 * The function is expected to return an INTEGER.
 * The function accepts following parameters:
 *  1. INTEGER n
 *  2. INTEGER k
 *  3. INTEGER r_q
 *  4. INTEGER c_q
 *  5. 2D_INTEGER_ARRAY obstacles
 */

int queensAttack(int n, int k, int r_q, int c_q, vector<vector<int>> obstacles) {
    // Directions: {row offset, col offset}
    vector<pair<int, int>> directions = {
        {-1,  0}, {1,  0}, {0, -1}, {0,  1}, 
        {-1, -1}, {-1,  1}, {1, -1}, {1,  1}
    };

    // Store obstacles for O(1) lookup
    set<pair<int, int>> obs;
    for (auto& o : obstacles) {
        obs.insert({o[0], o[1]});
    }

    int attackableSquares = 0;

    // Check each direction
    for (auto& dir : directions) {
        int r = r_q + dir.first;
        int c = c_q + dir.second;
        
        while (r >= 1 && r <= n && c >= 1 && c <= n && obs.find({r, c}) == obs.end()) {
            attackableSquares++;
            r += dir.first;
            c += dir.second;
        }
    }

    return attackableSquares;
}
int main()
{
    ofstream fout(getenv("OUTPUT_PATH"));

    string first_multiple_input_temp;
    getline(cin, first_multiple_input_temp);

    vector<string> first_multiple_input = split(rtrim(first_multiple_input_temp));

    int n = stoi(first_multiple_input[0]);

    int k = stoi(first_multiple_input[1]);

    string second_multiple_input_temp;
    getline(cin, second_multiple_input_temp);

    vector<string> second_multiple_input = split(rtrim(second_multiple_input_temp));

    int r_q = stoi(second_multiple_input[0]);

    int c_q = stoi(second_multiple_input[1]);

    vector<vector<int>> obstacles(k);

    for (int i = 0; i < k; i++) {
        obstacles[i].resize(2);

        string obstacles_row_temp_temp;
        getline(cin, obstacles_row_temp_temp);

        vector<string> obstacles_row_temp = split(rtrim(obstacles_row_temp_temp));

        for (int j = 0; j < 2; j++) {
            int obstacles_row_item = stoi(obstacles_row_temp[j]);

            obstacles[i][j] = obstacles_row_item;
        }
    }

    int result = queensAttack(n, k, r_q, c_q, obstacles);

    fout << result << "\n";

    fout.close();

    return 0;
}

string ltrim(const string &str) {
    string s(str);

    s.erase(
        s.begin(),
        find_if(s.begin(), s.end(), not1(ptr_fun<int, int>(isspace)))
    );

    return s;
}

string rtrim(const string &str) {
    string s(str);

    s.erase(
        find_if(s.rbegin(), s.rend(), not1(ptr_fun<int, int>(isspace))).base(),
        s.end()
    );

    return s;
}

vector<string> split(const string &str) {
    vector<string> tokens;

    string::size_type start = 0;
    string::size_type end = 0;

    while ((end = str.find(" ", start)) != string::npos) {
        tokens.push_back(str.substr(start, end - start));

        start = end + 1;
    }

    tokens.push_back(str.substr(start));

    return tokens;
}