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

public class Main {
	// -----------MyScanner class for faster input----------
	public static class MyScanner {
		BufferedReader br;
		StringTokenizer st;

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

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

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

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

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

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

	}
	// --------------------------------------------------------

	public static void main(String[] args) {
		MyScanner sc = new MyScanner();
		PrintWriter out = new PrintWriter(new BufferedOutputStream(System.out));

		long n = sc.nextLong();
		if (n % 2 == 0) {
			out.println(n / 2);
			out.close();
		} else if (n % 3 == 0) {
			out.println(n / 3);
			out.close();
		} else if (n % 5 == 0) {
			out.println(n / 5);
			out.close();
		} else {
			for (int i = 7; i < n; i+=2	) {
				if (n%i == 0) {
					out.println(n/i);	
					out.close();
					return;
				}
			}
		}

	}

}
