71分wa求助！

#include<bits/stdc++.h>
using namespace std;
int m,s,ans;
int tox[6]={0,0,1,-1};
int toy[6]={1,-1,0,0};
int die[305][305],vis[305][305];

struct po{
    int xx,yy,tt;
};

queue<po> q; 

int lala(int x,int y){
    if(die[x][y]==-1) return 99999;
    return die[x][y];
}

int main(){
    memset(die,-1,sizeof(die));
    cin>>m;
    vis[0][0]=1;
    for (int i=1,x,y,t;i<=m;++i){
        cin>>x>>y>>t;
        die[x][y]=t;
        for (int i=0;i<=3;++i){
            int nx=x+tox[i],ny=y+toy[i];
            if(nx>=0&&ny>=0&&(die[nx][ny]==-1||die[nx][ny]>t)) die[nx][ny]=t;
        }
    }
    q.push((po){0,0,0});
    while(!q.empty()){
        po now=q.front();
        q.pop();
        if(die[now.xx][now.yy]==-1){
            cout<<now.tt;
            return 0;
        }
        for (int i=0;i<=3;++i){
            po neww;
            neww.xx=now.xx+tox[i];
            neww.yy=now.yy+toy[i];
            neww.tt=now.tt+1;
            if(vis[neww.xx][neww.yy]==0&&neww.xx>=0&&neww.yy>=0&&neww.tt<lala(neww.xx,neww.yy)){
                // cout<<"/";
                vis[neww.xx][neww.yy]=1;
                q.push(neww);
            }
        }
    }
    cout<<-1;
    return 0;
}