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.
// INCLUDES
#include <iostream>
#include <sstream>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <cctype>
#include <string>
#include <vector>
#include <list>
#include <set>
#include <map>
#include <unordered_map>
#include <queue>
#include <stack>
#include <algorithm>
#include <functional>
#include<assert.h>
#include <ext/pb_ds/assoc_container.hpp> 
#include <ext/pb_ds/tree_policy.hpp>
//DEFINES
#define MAX 1000001
#define pii pair<int, int>
#define F first
#define S second
#define all(s) begin(s),end(s)
#define MIN3POS(a, b, c) (a) =< (b) ? ((a) =< (c) ? 1 : 3) : ((b) =< (c) ? 2 : 3)
#define MAX3POS(a,b,c) (a) >= (b) ? ((a) >= (c) ? 1 : 3) : ((b) >= (c) ? 2:3)
#define endl '\n'
#define int long long
#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
#define FOR(i, begin, end) for (__typeof(end) i = (begin) - ((begin) > (end)); i != (end) - ((begin) > (end)); i += 1 - 2 * ((begin) > (end)))
#define what_is(x) cerr << #x << 'is' << x << endl;
#define IOS   ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define error(args...) { string _s = #args; replace(_s.begin(), _s.end(), ',', ' '); stringstream _ss(_s); istream_iterator<string> _it(_ss); err(_it, args);}
//NAMESPACES
using namespace __gnu_pbds; 
using namespace std;
//HELPERS
void err(istream_iterator<string> it) {}
template<typename T, typename... Args>
void err(istream_iterator<string> it, T a, Args... args) {
cerr << *it << '=' << a << endl;
err(++it, args...);
}

vector<int> powers2(32,0);void initialize(){ for(int i=1;i<powers2.size();i++) powers2[i] = powers2[i-1]*2;}
int32_t main()
{
IOS
int n;
cin>>n;
int  d,flag=0;
for(int i=2;i*i<=n;i++){
    if(n%i == 0) {
        flag = 1;
        d=i;
    }
}
if(flag == 0)
cout<<1;
else {
    if(!(n&1))
    cout<<n/2;
    else cout<< 1+(n-d)/2;
}
return 0;
}
// Use emplace back in place of pushback
// Use tie function , for object destructuring