import java.util.*;
 
class C {
 
	public void run() {
		Scanner sc = new Scanner(System.in);
		while (sc.hasNext()) {
			int h = sc.nextInt();
			int w = sc.nextInt();
			int c = sc.nextInt();
			if ((h | w | c) == 0)
				return;
 
			int[][] p = new int[h][w];
			for (int i = 0; i < h; i++)
				for (int j = 0; j < w; j++)
					p[i][j] = sc.nextInt();
 
			int ans = 0;
			boolean[][][] mm = null;
			for (int t = 0; t < 1296; t++) {
				int[] cs = new int[5];
				for (int j = 0, k = t; j < 4; j++, k /= 6)
					cs[j] = k % 6 + 1;
				cs[4] = c;
				boolean[][][] map = new boolean[6][h][w];
				dfs(0, 0, p[0][0], p, map[0]);
				for (int k = 0; k < 5; k++)
					for (int i = 0; i < h; i++)
						for (int j = 0; j < w; j++)
							if (map[k][i][j])
								dfs(i, j, cs[k], p, map[k + 1]);
				int res = 0;
				for (int i = 0; i < h; i++)
					for (int j = 0; j < w; j++)
						if (map[5][i][j])
							res++;
				ans = Math.max(ans, res);
				if (ans == res)
					mm = map;
			}
//			for (int k = 0; k <= 5; k++)
//				for (int i = 0; i < h; i++) {
//					for (int j = 0; j < w; j++)
//						System.out.print((mm[k][i][j] ? "1" : "0") + " ");
//					System.out.println();
//				}
			System.out.println(ans);
		}
	}
 
	static final int[] di = { 1, 0, -1, 0 };
	static final int[] dj = { 0, 1, 0, -1 };
 
	private void dfs(int i, int j, int c, int[][] p, boolean[][] map) {
		map[i][j] = true;
		for (int d = 0; d < 4; d++) {
			int ni = i + di[d];
			int nj = j + dj[d];
			if (0 <= ni && ni < p.length && 0 <= nj && nj < p[0].length)
				if (p[ni][nj] == c && !map[ni][nj])
					dfs(ni, nj, c, p, map);
		}
	}
 
	public static void main(String[] args) throws Exception {
		new C().run();
	}
}

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MyA1IDUKMSA2IDMgMiA1CjIgNSA0IDYgMQoxIDIgNCAxIDUKNCA1IDYKMSA1IDYgMSAyCjEgNCA2IDMgMgoxIDUgMiAzIDIKMSAxIDIgMyAyCjEgMSA1CjEKMSA4IDYKMSAyIDMgNCA1IDEgMiAzCjggMSAxCjEKMgozCjQKNQoxCjIKMwo4IDggNgo1IDIgNSAyIDYgNSA0IDIKNCAyIDIgMiA1IDIgMiAyCjQgNCA0IDIgNSAyIDIgMgo2IDQgNSAyIDIgMiA2IDYKNiA2IDUgNSAyIDIgNiA2CjYgMiA1IDQgMiAyIDYgNgoyIDQgNCA0IDYgMiAyIDYKMiAyIDIgNSA1IDIgMiAyCjggOCAyCjMgMyA1IDQgMSA2IDIgMwoyIDMgNiA0IDMgNiAyIDIKNCAxIDYgNiA2IDQgNCA0CjIgNSAzIDYgMyA2IDMgNQozIDEgMyA0IDEgNSA2IDMKMSA2IDYgMyA1IDEgNSAzCjIgNCAyIDIgMiA2IDUgMwo0IDEgMyA2IDEgNSA1IDQKMCAwIDAK

3 5 5
1 6 3 2 5
2 5 4 6 1
1 2 4 1 5
4 5 6
1 5 6 1 2
1 4 6 3 2
1 5 2 3 2
1 1 2 3 2
1 1 5
1
1 8 6
1 2 3 4 5 1 2 3
8 1 1
1
2
3
4
5
1
2
3
8 8 6
5 2 5 2 6 5 4 2
4 2 2 2 5 2 2 2
4 4 4 2 5 2 2 2
6 4 5 2 2 2 6 6
6 6 5 5 2 2 6 6
6 2 5 4 2 2 6 6
2 4 4 4 6 2 2 6
2 2 2 5 5 2 2 2
8 8 2
3 3 5 4 1 6 2 3
2 3 6 4 3 6 2 2
4 1 6 6 6 4 4 4
2 5 3 6 3 6 3 5
3 1 3 4 1 5 6 3
1 6 6 3 5 1 5 3
2 4 2 2 2 6 5 3
4 1 3 6 1 5 5 4
0 0 0