1 #include <iostream>
 2 #include <cstdio>
 3 #include <algorithm>
 4 #include <vector>
 5 #include <queue>
 6 #include <cstring>
 7 #include <climits>
 8 using namespace std;
 9 
10 int m;
11 int const maxn = 302;
12 int const mde = 50004;
13 struct node
14 {
15     int x, y, t;
16     bool operator < (const node that) const {
17         return t < that.t;
18     }
19     node() {x = y = t = 0;}
20 };
21 int mp[maxn][maxn];
22 int dir[4][2] = {0, 1, 0, -1, 1, 0, -1, 0};
23 bool border(int x, int y)
24 {
25     if(x < 0 || y < 0 || y > 301 || x > 301) return false;
26     return true;
27 }
28 void init()
29 {
30     for(int i = 0; i < maxn; i++) {
31         for(int j = 0; j < maxn; j++) mp[i][j] = INT_MAX;
32     }
33     for(int i = 0; i < m; i++) {
34         int a, b, c; scanf("%d%d%d", &a, &b, &c);
35         if(c < mp[a][b]) mp[a][b] = c;
36         for(int j = 0; j < 4; j++) {
37             int dx = a + dir[j][0], dy = b + dir[j][1];
38             if(border(dx, dy) && c < mp[dx][dy]) mp[dx][dy] = c;
39         }
40     }
41 }
42 void bfs(int &ans)
43 {
44     queue<node> q; node rec;
45     q.push(rec);
46     if(mp[0][0] == 0) return;
47     bool inq[maxn][maxn]; memset(inq, 0, sizeof(inq)); inq[0][0] = 1;
48     while(!q.empty()) {
49         rec = q.front(); q.pop();
50         if(mp[rec.x][rec.y] == INT_MAX) {ans = rec.t; return; }
51         for(int i = 0; i < 4; i++) {
52             node dn; dn.x = rec.x + dir[i][0]; dn.y = rec.y + dir[i][1]; dn.t = rec.t + 1;
53             if(border(dn.x, dn.y) && mp[dn.x][dn.y] > dn.t && !inq[dn.x][dn.y]) {
54                 q.push(dn);
55                 inq[dn.x][dn.y] = 1;
56             }
57         }
58     }
59 }
60 void work()
61 {
62     int ans = -1;
63     init();
64     bfs(ans);
65     printf("%d\n", ans);
66 }
67 int main()
68 {
69     while(scanf("%d", &m) != EOF) work();
70     return 0;
71 }