BAEKJOON_1149

import java.io.*;
import java.sql.Array;
import java.util.*;


public class Main {

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));

        int N = Integer.parseInt(br.readLine());

        int[][] house = new int[N+1][3];
        int[][] D = new int[N+1][3];
        StringTokenizer st;
        for (int i = 1; i < N+1; i++) {
            st = new StringTokenizer(br.readLine());
            for (int j = 0; j < 3; j++) {
                house[i][j] = Integer.parseInt(st.nextToken());
            }
        }

        for (int i = 1; i <= N; i++) {
            D[i][0] = Math.min(D[i - 1][1], D[i - 1][2]) + house[i][0];
            D[i][1] = Math.min(D[i - 1][0], D[i - 1][2]) + house[i][1];
            D[i][2] = Math.min(D[i - 1][0], D[i - 1][1]) + house[i][2];

        }

        bw.write(String.valueOf(Math.min(Math.min(D[N][0], D[N][1]), D[N][2])));
        bw.flush();
        bw.close();
    }
}