static int[] dc = {0, 0, 1, -1};

static int[] dr = {-1, 1, 0, 0};

static int[][] map;

static int[][] visited;

static int N;

static int M;

public static void main(String[] args) throws IOException {

BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

StringTokenizer st = new StringTokenizer(br.readLine());

N = Integer.parseInt(st.nextToken());

M = Integer.parseInt(st.nextToken());

int K = Integer.parseInt(st.nextToken());

map = new int[N][M];

visited = new int[N][M];

int MAX_Trash = 0;

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

st = new StringTokenizer(br.readLine());

int c = Integer.parseInt(st.nextToken());

int r = Integer.parseInt(st.nextToken());

map[c - 1][r - 1] = 1;

}

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

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

if (map[i][j] == 1) {

int c= BFS(i, j,1);

MAX_Trash=Math.max(MAX_Trash,c);

}

}

}

System.out.println(MAX_Trash);

}

private static int BFS(int col, int row, int count) {

Deque<int[]> dq = new LinkedList<>();

dq.offer(new int[]{col, row});

visited[col][row] = 1;

while (!dq.isEmpty()) {

int[] now = dq.pollFirst();

int nc = now[0];

int nr = now[1];

for (int i = 0; i < 4; i++) {

int cc = dc[i] + nc;

int cr = dr[i] + nr;

if (0 <= cc && cc < N && 0 <= cr && cr < M) {

if (map[cc][cr] == 1 && visited[cc][cr]==0) {

count++;

visited[cc][cr]=1;

dq.offer(new int[]{cc, cr});

}

}

}

}

return count;

}

}