#include<bits/stdc++.h>
using namespace std;
int a[505][505];//记录每个点流星砸下的时间
int t[505][505];//记录奶牛走到每个点所需的时间
struct node { int x, y; };
queue<node> qu;
int dx[5] = { -1,0,0,1 };
int dy[5] = { 0,-1,1,0 };
int M;
int now;
int main() {
	cin >> M;
	memset(a, -1, sizeof(a));
	for (int i = 1; i <= M; i++)
	{
		int x, y, time;
		cin >> x >> y >> time;
		if (a[x][y] == -1 || time <= a[x][y])
		{
			a[x][y] = time;
			for (int j = 0; j < 4; j++)
			{
				int nx = x + dx[j], ny = y + dy[j];
				if (nx >= 0 && ny >= 0 && (time < a[nx][ny] || a[nx][ny] == -1))a[nx][ny] = time;
			}
		}
	}
	qu.push({ 0,0 });
	t[0][0] = 0;
	if (a[0][0] == -1)
	{
		cout << 0;
		return 0;
	}
	while (!qu.empty())
	{
		int x0 = qu.front().x, y0 = qu.front().y;
		qu.pop();
		for (int i = 0; i < 4; i++)
		{
			int nx = x0 + dx[i], ny = y0 + dy[i];
			if (nx >= 0 && ny >= 0 && (a[nx][ny] > t[x0][y0] + 1 || a[nx][ny] == -1))
			{
				t[nx][ny] = t[x0][y0] + 1;
				if (a[nx][ny] == -1)
				{
					cout << t[nx][ny];
					return 0;
				}
				qu.push({ nx,ny });
			}
		}
	}
	cout << -1;
	return 0;
}