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.
//package All_in_all;

import java.io.*;

/**
 * Created by nikitos on 25.08.17.
 */


public class simvoli {

    public StreamTokenizer t;

    private class Pair implements Comparable<Pair> {
        int from;
        int to;

        private Pair(int from, int to) {
            this.from = from;
            this.to = to;
        }

        @Override
        public int compareTo(Pair o) {
            if (this.from == o.from && this.to == o.to)
                return 0;

            if (this.from > o.from || this.from == o.from && this.to > o.to)
                return 1;

            return -1;
        }
    }

    public int nextInt() throws IOException {
        t.nextToken();
        return (int) t.nval;
    }

    public long nextLong() throws IOException {
        t.nextToken();
        return (long) t.nval;
    }

    public String nextString() throws IOException {
        t.nextToken();
        return t.sval;
    }

    public void start() throws IOException {
        t = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));

        int n = nextInt();

        int count = 0;
        int del;
        do {
            del = getDel(n);
            n -= del;
            ++count;
        } while (n != 0);

        System.out.println(count);
    }

    private int getDel(int n) {
        for (int i = 2; i < Math.sqrt(n) + 5; i++) {
            if (n % i == 0) {
                return i;
            }
        }

        return n % 2 == 0? 1 : n;
    }

    public static void main(String[] args) throws IOException {
        new simvoli().start();
    }

}
