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

public class AmrAndPins {
	public static void main(String[] args) {
		MyScanner sc = new MyScanner();
		
		long R = sc.nextLong();
		long X = sc.nextLong();
		long Y = sc.nextLong();
		long XP = sc.nextLong();
		long YP = sc.nextLong();
		
		long dx = XP - X;
		long dy = YP - Y;
		double d = Math.sqrt((dx * dx) + (dy * dy));
		
		System.out.println((int)Math.ceil(d / (2 * R)));
	}

	public static class MyScanner {
		BufferedReader br;
		StringTokenizer st;

		public MyScanner() {
			br = new BufferedReader(new InputStreamReader(System.in));
		}

		int nextInt() {
			return Integer.parseInt(next());
		}
		
		int[] nextIntArray(int n) {
			int[] arr = new int[n];
			for (int i = 0; i < n; i++) {
				arr[i] = nextInt();
			}
			return arr;
		}

		long nextLong() {
			return Long.parseLong(next());
		}

		double nextDouble() {
			return Double.parseDouble(next());
		}

		String next() {
			while (st == null || !st.hasMoreElements()) {
				try {
					st = new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			return st.nextToken();
		}

		String nextLine() {
			String str = "";
			try { str = br.readLine(); }
			catch (IOException e) { e.printStackTrace(); }
			return str;
		}
	}
}