#include <bits/stdc++.h>
#define endl '\n'
#define int long long
 
using namespace std;
 
void solve()
{
int x;
cin>>x;
cout<<(x>>1);
}
 
int32_t main()
{
#ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int Test=1;
    //cin >> Test;
    for (int i = 0; i < Test; ++i) {
        solve();
    }
    cerr << "Done!" << endl;
    return 0;
}

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10