c语言wa71%，求助大佬

#include<stdio.h>
int book[310][310], book1[310][310], book2[310][310], nest[4][2] = { {0,1},{1,0},{-1,0},{0,-1} };
struct nb {
    int x;
    int y;
    int s;
} a[90020];
int main()
{
    int n, i, j;
    scanf("%d", &n);
    memset(book1, 100, sizeof(book1));
    for (i = 1; i <= n; i++)
    {
        int g, k, h;
        scanf("%d %d %d", &g,&k,&h);
        if (book1[g][k] > h);
            book1[g][k] = h;
        book2[g][k] = 1;
        for (j = 0; j <= 3; j++)
        {
            int tx = g + nest[j][0];
            int ty = k + nest[j][1];
            if (tx < 0 || tx>300 || ty < 0 || ty>300)
                continue;
            if (book1[tx][ty] > h)
                book1[tx][ty] = h;
            book2[tx][ty] = 1;
        }
    }
    if (book2[0][0] == 0)
    {
        printf("0\n");
        return 0;
    }
    int hard = 1, tail = 1;
    a[tail].x = 0;
    a[tail].y = 0;
    a[tail].s = 0;
    book[0][0] = 1;
    tail++;
    int flag = 0;
    while (hard < tail)
    {
        for (i = 0; i <= 3; i++)
        {
            int tx = a[hard].x + nest[i][0];
            int ty = a[hard].y + nest[i][1];
            if (tx < 0 || tx>300 || ty < 0 || ty>300)
                continue;
            if (a[hard].s + 1 >= book1[tx][ty])
                continue;
            if (book[tx][ty] == 0)
            {
                a[tail].x = tx;
                a[tail].y = ty;
                a[tail].s = a[hard].s + 1;
                book[tx][ty] = 1;
                tail++;
            }
            if (book2[tx][ty] == 0)
            {
                flag = 1;
                break;
            }
        }
        if (flag == 1)
        {
            break;
        }
        hard++;
    }
    if (flag == 1)
        printf("%d\n", a[tail - 1].s);
    else
        printf("-1\n");
    return 0;
}