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


public class CircleCenter {
    public static void main(String[] args) throws IOException {
        BufferedReader scanner = new BufferedReader(new InputStreamReader(System.in));
            StringTokenizer tokenizer = new StringTokenizer(scanner.readLine());
            long r = Long.parseLong(tokenizer.nextToken());
            long x = Long.parseLong(tokenizer.nextToken());
            long y = Long.parseLong(tokenizer.nextToken());
            long xx = Long.parseLong(tokenizer.nextToken());
            long yy = Long.parseLong(tokenizer.nextToken());
            
            long distance = (long)Math.ceil(Math.sqrt((xx - x) * (xx - x) + (yy - y) * (yy - y)));
            long rotations = distance / (2 * r);
            if(distance % (2 * r) != 0){
                    rotations++;
            }
            
            System.out.println(rotations);
    }
}
