import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.StringTokenizer;

public class tetris_va {
    public static void main(String[] args) {
        new tetris_va().run();
    }

    BufferedReader br;
    StringTokenizer st;
    PrintWriter out;

    public String nextToken() throws IOException {
        while (st == null || !st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }

    public int nextInt() throws IOException {
        return Integer.parseInt(nextToken());
    }

    public int solve(int a, int b, int c) {
        int ans = 2 * a;
        if (c >= 2) {
            ans += 2 * b + 3;
            ans += (c - 2) / 2 * 3;
        }
        return ans;
    }

    public void run() {
        try {
            br = new BufferedReader(new InputStreamReader(System.in));
            out = new PrintWriter(System.out);

            out.println(solve(nextInt(), nextInt(), nextInt()));

            out.close();
        } catch (IOException e) {
        }
    }
}