import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;

public class Main{

	static int[][] plane;
	static Queue<Point> queue = new LinkedList<Point>();
	static int[] dx = { 1, 0, -1, 0 };
	static int[] dy = { 0, 1, 0, -1 };
	static boolean[][] visited;
	static final int INF = 100000;

	public static void main(String[] args) {
		plane = new int[310][310];
		visited = new boolean[310][310];
		for (int i = 0; i < plane.length; i++) {
			for (int j = 0; j < plane[0].length; j++) {
				plane[i][j] = INF;
			}
		}
		Scanner scan = new Scanner(System.in);
		int line = scan.nextInt();
		for (int i = 0; i < line; i++) {
			int x = scan.nextInt();
			int y = scan.nextInt();
			int t = scan.nextInt();
			plane[x][y] = t;
			for (int j = 0; j < 4; j++) {
				int xx = x + dx[j];
				int yy = y + dy[j];
				if (xx >= 0 && yy >= 0 && plane[xx][yy] > t) {
					plane[xx][yy] = t;
				}
			}
		}
		scan.close();
		queue.add(new Point(0, 0, 0));
		System.out.println(bfs());
	}

	static int bfs() {
		Point p = queue.poll();
		visited[p.x][p.y] = true;
		if (p.depth >= plane[p.x][p.y]) {
			return -1;
		}
		while (p != null) {
			int steps = p.depth;

			if (plane[p.x][p.y] == INF) {
				return steps;
			}
			for (int i = 0; i < 4; i++) {
				int xx = p.x + dx[i];
				int yy = p.y + dy[i];
				if (xx >= 0 && yy >= 0 && steps + 1 < plane[xx][yy]
						&& !visited[xx][yy]) {
					visited[xx][yy] = true;
					queue.add(new Point(xx, yy, steps + 1));
				}
			}
			p = queue.poll();
		}
		return -1;
	}
}

class Point {
	int x;
	int y;
	int depth;

	Point(int x, int y, int depth) {
		this.x = x;
		this.y = y;
		this.depth = depth;
	}
}