import java.io.*;
import java.util.*;
import java.util.stream.*;

// 処理
class Process {
    private int N;

    Process(int N) {
        this.N = N;
    }

    int getResult() {
        return ((N % 2 == 0) ? N : (N - 1));
    }
}

public class Main {
    public static void main(String[] args) throws IOException {
        var bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        var printWriter    = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));

        // 入力
        int N = Integer.parseInt(bufferedReader.readLine().trim());

        // 出力
        printWriter.println((new Process(N)).getResult());

        bufferedReader.close();
        printWriter.close();
    }
}