#include<bits/stdc++.h>
using namespace std;
#define yes cout<<"YES"<<"\n";
#define no cout<<"NO"<<"\n";
#define forn  for(int i=0;i<n;i++);
#define acin  for(int i=0;i<n;i++)cin>>arr[i];
#define v vector<int>arr(n);
#define int long long 

int32_t main()
{
   int n;
   cin>>n;
  for(int i=n;i>=0;i--){
    if(i%2==0){cout<<i<<endl;break;}
  }



}