// 112
#include <bits/stdc++.h>
using namespace std;
int n, d;
struct node
{
    int x, y;
    int xl, xr;
    const bool operator<(node b) const
    {
        return xr > b.xr;
    }
} is[1005];
int main()
{
    scanf("%d%d", &n, &d);
    int minl = INT_MAX, maxl = INT_MIN;
    for (int i = 1; i <= n; ++i)
    {
        scanf("%d%d", &is[i].x, &is[i].y);
        if (is[i].y > d)
        {
            puts("-1");
            return 0;
        }
        is[i].xl = is[i].x - sqrt(d * d - is[i].y * is[i].y);
        is[i].xr = is[i].x + sqrt(d * d - is[i].y * is[i].y);
        minl = min(minl, is[i].xl);
        maxl = max(maxl, is[i].xr);
    }
    sort(is + 1, is + n + 1, [](node x, node y)
         { return x.xl < y.xl; });
    int ans = 0, now = 1;
    int maxans = 0;
    priority_queue<node> q;
    for (int t = minl; t <= maxl; ++t)
    {
        while (!q.empty() && q.top().xr < t)
            q.pop();
        while (now <= n && is[now].xl >= t)
        {
            q.push(is[now++]);
            maxans = max(maxans, (int)q.size());
        }
    }
    printf("%d\n", maxans);
    return 0;
}