import java.util.*;

public class LastDayToCross {

private int[][] directions = new int[][]{{1, 0}, {-1, 0}, {0, 1}, {0, -1}};

public boolean canCross(int row, int col, int[][] cells, int day) {

int[][] grid = new int[row][col];

Queue<int[]> queue = new LinkedList<>();

for (int i = 0; i < day; i++) {

grid[cells[i][0] - 1][cells[i][1] - 1] = 1;

}

for (int i = 0; i < col; i++) {

if (grid[0][i] == 0) {

queue.offer(new int[]{0, i});

grid[0][i] = -1;

}

}

while (!queue.isEmpty()) {

int[] cur = queue.poll();

int r = cur[0], c = cur[1];

if (r == row - 1) {

return true;

}

for (int[] dir : directions) {

int newRow = r + dir[0];

int newCol = c + dir[1];

if (newRow >= 0 && newRow < row && newCol >= 0 && newCol < col && grid[newRow][newCol] == 0) {

grid[newRow][newCol] = -1;

queue.offer(new int[]{newRow, newCol});

}

}

}

return false;

}

public int latestDayToCross(int row, int col, int[][] cells) {

int left = 1;

int right = cells.length;

while (left < right) {

int mid = right - (right - left) / 2;

if (canCross(row, col, cells, mid)) {

left = mid;

} else {

right = mid - 1;

}

}

return left;

}

public static void main(String[] args) {

Scanner scanner = new Scanner(System.in);

System.out.print("Enter the number of rows: ");

int row = scanner.nextInt();

System.out.print("Enter the number of columns: ");

int col = scanner.nextInt();

System.out.print("Enter the number of cells: ");

int n = scanner.nextInt();

int[][] cells = new int[n][2];

System.out.println("Enter the cells' coordinates:");

for (int i = 0; i < n; i++) {

System.out.print("Cell " + (i + 1) + ": ");

cells[i][0] = scanner.nextInt();

cells[i][1] = scanner.nextInt();

}

LastDayToCross solution = new LastDayToCross();

int lastDay = solution.latestDayToCross(row, col, cells);

System.out.println("The last day where it is possible to walk from the top to the bottom: " + lastDay);

}

}