import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
import java.util.StringTokenizer;
import java.lang.StringBuilder;
import java.lang.Math;
import java.util.HashMap;
import java.util.Arrays;
public class Main{
    public static void main(String[] args) throws IOException{
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());
        long r =  (long)Integer.parseInt(st.nextToken());
        long x1 = (long)Integer.parseInt(st.nextToken());
        long y1 = (long)Integer.parseInt(st.nextToken());
        long x2 = (long)Integer.parseInt(st.nextToken());
        long y2 = (long)Integer.parseInt(st.nextToken());
        System.out.print((int)Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2))/(2*r)+(Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2))%(2*r)==0?0:1));
    }
}
