For problem statement at 0-999/200-299/200-209/203/problemB.txt this is a correct solution, but verifier at 0-999/200-299/200-209/203/verifierB.go ends with All 100 tests passed can you fix the verifier? package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	reader := bufio.NewReader(os.Stdin)
	var n, m int
	if _, err := fmt.Fscan(reader, &n, &m); err != nil {
		return
	}

	grid := make([][]bool, n+1)
	for i := range grid {
		grid[i] = make([]bool, n+1)
	}

	for i := 1; i <= m; i++ {
		var x, y int
		fmt.Fscan(reader, &x, &y)
		grid[x][y] = true

		for r := x - 2; r <= x; r++ {
			for c := y - 2; c <= y; c++ {
				if r >= 1 && r+2 <= n && c >= 1 && c+2 <= n {
					if grid[r][c] && grid[r][c+1] && grid[r][c+2] &&
						grid[r+1][c] && grid[r+1][c+1] && grid[r+1][c+2] &&
						grid[r+2][c] && grid[r+2][c+1] && grid[r+2][c+2] {
						fmt.Println(i)
						return
					}
				}
			}
		}
	}
	fmt.Println("-1")
}