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

public class HEIGHT {
	public static void main(String[] args) throws IOException {
		// TODO Auto-generated method stub
		InputReader sc = new InputReader(System.in);
		long n = sc.nextLong();
		for (int i = 2; i < Math.sqrt(n)+1; i++) {
			if (n % i == 0) {
				System.out.println((n - i) / 2 + 1);
				return;
			}
		}
		System.out.println(1);
	}

	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());
		}
	}
}
