import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.Scanner;

public class Main {

    private static final InputStreamReader standardInput = new InputStreamReader(System.in);
    private static final BufferedReader bufferedReader = new BufferedReader(standardInput);
    private static final Scanner scanner = new Scanner(bufferedReader);

    private static final OutputStreamWriter standardOutput = new OutputStreamWriter(System.out);
    private static final BufferedWriter bufferedWriter = new BufferedWriter(standardOutput);
    private static final PrintWriter printWriter = new PrintWriter(bufferedWriter);

    public static void main(String[] args) {
        long r = scanner.nextLong();
        long x1 = scanner.nextLong();
        long y1 = scanner.nextLong();
        long x2 = scanner.nextLong();
        long y2 = scanner.nextLong();
        printWriter.println(getMinimumSteps(r, x1, y1, x2, y2));
        printWriter.flush();
        scanner.close();
    }

    private static long getMinimumSteps(long r, long x1, long y1, long x2, long y2) {
        double d = Math.sqrt(((x2 - x1) * (x2 - x1)) + ((y2 - y1) * (y2 - y1)));
        if ((int) d == d && (int) d % (2 * r) == 0) {
            return (int) d / (2 * r);
        } else {
            return 1 + (int) (d / (2 * r));
        }
    }
}
