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1076B.cpp
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1076B.cpp
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#include<iostream>
#include<vector>
#include<string>
#include<cstring>
#include<stack>
#include<queue>
#include<cstdio>
#include<set>
#include<unordered_set>
#include<cmath>
#include<algorithm>
#include<functional>
#include<utility>
#include<cstdlib>
using namespace std;
typedef long long int lli;
typedef size_t idx;
#define vi vector<int>
#define pb(n) push_back(n)
#define ln "\n"
#define sp ends
#define newline cout << ln
const int MOD = 1000000007;
#define fastios ios_base::sync_with_stdio(false); cin.tie(0)
lli trial(lli n){
for(lli d = 3; d * d <= n; d += 2){
if(n == 1) break;
while(!(n % d)){
return d;
}
}
return n;
}
int main(){
#ifndef ONLINE_JUDGE
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif
lli n;
cin >> n;
if(!(n % 2)) cout << n / 2 << ln;
else{
n -= trial(n);
cout << (n / 2) + 1 << ln;
}
return 0;
}