/// Abdur Rahman Salman ///

#include<bits/stdc++.h>
using namespace std;

#define endl "\n"
#define trace(x) cout << #x << ": " << x << endl
int32_t main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    int n; cin >> n;
    if(n % 2 == 0) cout << n << endl;
    else cout << n - 1 << endl;
    return 0;
}