import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;


public class CircleCenter {
    public static long numberOfSteps(int r, int x, int y, int xx, int yy) {
        long distance = (long)Math.ceil(getDistance(x, y, xx, yy));
        long rotations = distance / (2 * r);
        if(distance % (2 * r) != 0){
                rotations++;
        }
        return rotations;
    }
    
    public static double getDistance(long x, long y, long xx, long yy) {
        return Math.sqrt((xx - x) * (xx - x) + (yy - y) * (yy - y));
    }
    
    public static void main(String[] args) {
        BufferedReader scanner = new BufferedReader(new InputStreamReader(System.in));
        try {
            StringTokenizer tokenizer = new StringTokenizer(scanner.readLine());
            int r = Integer.parseInt(tokenizer.nextToken());
            int x = Integer.parseInt(tokenizer.nextToken());
            int y = Integer.parseInt(tokenizer.nextToken());
            int xx = Integer.parseInt(tokenizer.nextToken());
            int yy = Integer.parseInt(tokenizer.nextToken());
            
            System.out.println(numberOfSteps(r, x, y, xx, yy));
            
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}
