public static void main(String[] args) {

Scanner scanner = new Scanner(System.in);

int N = scanner.nextInt();

int K = scanner.nextInt();

int[][] matrix = new int[N][N];

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

for (int j = 0; j < N; j++) {

matrix[i][j] = scanner.nextInt();

}

}

for (int i = 0; i <= N / 2; i++) {

if (matrix[i][N / 2 - i] != K || matrix[i][N / 2 + i] != K) {

System.out.println("NO");

return;

}

}

for (int j = 0; j < N; j++) {

if (matrix[N / 2][j] != K) {

System.out.println("NO");

return;

}

}

System.out.println("YES");

}