usaco why did the cow cross the road iii silver java

1//sample input
23 3 3
32 2 2 3
43 3 3 2
53 3 2 3
63 3
72 2
82 3
9//CODE (2021/1/18) YY/MM/DD
10  import java.util.*;
11import java.io.*;
12public class Main {
13    static  field[][] farm;
14  public static void main(String[] args) throws Exception {
15    Scanner sc = new Scanner (new File("countcross.in"));
16    int n = sc.nextInt();//n x n grid
17    int k = sc.nextInt();// k cows
18    int r = sc.nextInt();// r roads
19     farm = new field[n][n];
20    for (int i = 0; i < n; i++) Arrays.fill(farm[i], new field());
21    for (int i = 0; i < r; i++) setRoad(new position(sc.nextInt(), sc.nextInt()), 
22                                        new position(sc.nextInt(), sc.nextInt()));
23    //floodFill
24    int no1 = 0;
25    for (int x = 0; x < n; x++ ){
26        for (int y = 0; y < n; y++){
27            if (!farm[x][y].visited){
28                floodFill(x, y, farm[x][y], no1);
29                no1++;
30            }
31        }
32    }
33    no1--;
34    int[] cows = new int[no1];
35    
36    for (int i = 0; i < k; i++){
37        int x = sc.nextInt();
38        int y = sc.nextInt();
39        int index = farm[x-1][y-1].fieldNum;
40        cows[index - 1]++;
41    }
42    int answer = 0; 
43    for (int i = 1; i < cows.length; i++){// when i = 0, it is in the default group, which means that it requires no road.
44        answer += k - cows[i];
45    }
46    PrintWriter out = new PrintWriter(new File("countcross.out"));
47    out.println(answer);
48    out.close();
49    sc.close();
50  }
51  static void floodFill(int x, int y, field thisF, int no1){
52      if (x < 0 || y < 0 || x >= farm.length || y >= farm[0].length) return; // Out of bound
53      if (thisF.visited) return; //visited
54      thisF = farm[x][y];
55      thisF.visited = true;
56      thisF.fieldNum = no1;
57      if (!thisF.fence[field.north]) floodFill(x, y+1, farm[x][y], no1);
58      if (!thisF.fence[field.south]) floodFill(x, y-1, farm[x][y], no1);
59      if (!thisF.fence[field.east]) floodFill(x+1, y, farm[x][y], no1);
60      if (!thisF.fence[field.west]) floodFill(x-1, y, farm[x][y], no1);
61  }
62  static void setRoad(position from, position to){
63      int dirF = from.pointTo(to);
64      int dirT = to.pointTo(from);
65      farm[from.x - 1][from.y - 1].fence[dirF] = true;
66      farm[to.x - 1][to.y - 1].fence[dirT] = true;
67  }
68}
69class field {
70    public boolean visited = false;
71    public int fieldNum = -1;
72    public boolean[] fence = new boolean[4];//NSWE
73    public field(){
74
75    }
76   static final int north = 0;
77   static final int south = 1;
78   static final int west = 2;
79   static final int east = 3;
80}
81class position {
82    public int x;
83    public int y;
84    public position(int x, int y){
85        this.x = x;
86        this.y = y;
87    }
88    public int pointTo(position a){
89        if (a.x > this.x) return field.east; if (a.x < this.x) return field.west;//x
90        if (a.y > this.y) return field.north; if (a.y < this.y) return field.south;//y
91        System.out.println("ERROR: poinTo");
92        return -1;
93    
94    }
95}
96//Output:
97     2