#include<bits/stdc++.h>
using namespace std;

struct Point {
    int x;
    int y;
};

bool comparePoints(const Point& p1, const Point& p2) {
    return (p1.x < p2.x) || (p1.x == p2.x && p1.y < p2.y);
}

int main() {
    int s, n;
    cin >> s >> n;

    vector<Point> fish(n);
    for (int i = 0; i < n; i++) {
        cin >> fish[i].x >> fish[i].y;
    }

    sort(fish.begin(), fish.end(), comparePoints);

    int maxFish = 0;
    for (int i = 0; i < n; i++) {
        int fishCount = 1;

        for (int j = i + 1; j < n; j++) {
            if (fish[j].x - fish[i].x > s) {
                break;
            }
            if (fish[j].y >= fish[i].y && fish[j].y <= fish[i].y + s) {
                fishCount++;
            }
        }

        for (int j = i - 1; j >= 0; j--) {
            if (fish[i].x - fish[j].x > s) {
                break;
            }
            if (fish[j].y >= fish[i].y && fish[j].y <= fish[i].y + s) {
                fishCount++;
            }
        }

        maxFish = max(maxFish, fishCount);
    }

    cout << maxFish << "\n";

    return 0;
}