diff --git a/28.cpp b/28.cpp
new file mode 100644
index 0000000..b5f2c74
--- /dev/null
+++ b/28.cpp
@@ -0,0 +1,48 @@
+// 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;
+}
\ No newline at end of file