Lifeguard

Children are spending their holidays at the seaside, and right now they are all bathing in the water. A lifeguard keeps them safe, and his range of sight is $k$ meters. Anyone located more than $k$ meters away from the lifeguard is invisible to him. Given the positions of the lifeguard and the children, determine how many children would not receive help if something dangerous happened.

The first line contains integers $n$, $k$, $x$, $y$ ($1 \le n, k \le 100000$, $0 \le x, y \le 10000$), denoting the number of children, the lifeguard's range of sight, and the lifeguard's position $(x, y)$, respectively. Each of the next $n$ lines contains two integers $x_i$ and $y_i$ ($0 \le x_i, y_i \le 10000$), the coordinates of the $i$-th child. (The bathing area is described on a coordinate plane.)

Print, on a single line, the number of children who cannot feel safe, that is, the number of children who lie outside the lifeguard's range of sight.