You are given an integer number n. The following algorithm is applied to it:

  1. if n = 0, then end algorithm; 
  2. find the smallest prime divisor d of n; 
  3. subtract d from n and go to step 1. 



Determine the number of subtrations the algorithm will make.

Input

The only line contains a single integer n (2 ≤ n ≤ 10^{10}).

Output

Print a single integer — the number of subtractions the algorithm will make.

Examples

Input


5


Output


1


Input


4


Output


2

Note

In the first example 5 is the smallest prime divisor, thus it gets subtracted right away to make a 0.

In the second example 2 is the smallest prime divisor at both steps.

import java.io.*;
import java.util.*;

public class Educational_Codeforces_Round_54_B {

	public static void main(String[] args) {
		InputReader reader = new InputReader(System.in);
		long number = reader.nextLong(), count = 0;
		if (number % 2 == 0) {
			count += number / 2;
		} else {
			boolean check = false;
			for (long i = 3; i * i < number; i += 2) {
				if (number % i == 0) {
					count += (number - i) / 2 + 1;
					check = true;
					break;
				}
			}
			if (!check) {
				count++;
			}
		}
		System.out.print(count);
	}

	static class InputReader {

		StringTokenizer tokenizer;
		BufferedReader reader;
		String token;
		String temp;

		public InputReader(InputStream stream) {
			tokenizer = null;
			reader = new BufferedReader(new InputStreamReader(stream));
		}

		public InputReader(FileInputStream stream) {
			tokenizer = null;
			reader = new BufferedReader(new InputStreamReader(stream));
		}

		public String nextLine() throws IOException {
			return reader.readLine();
		}

		public String next() {
			while (tokenizer == null || !tokenizer.hasMoreTokens()) {
				try {
					if (temp != null) {
						tokenizer = new StringTokenizer(temp);
						temp = null;
					} else {
						tokenizer = new StringTokenizer(reader.readLine());
					}

				} catch (IOException e) {
				}
			}
			return tokenizer.nextToken();
		}

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

		public int nextInt() {
			return Integer.parseInt(next());
		}

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

	}
}
