import java.io.*;

import java.util.*;

public class lake {

public static int findin2D(ArrayList<int[]> a,int[] wanna) {

for(int i=0;i<a.size();i++) {

if(a.get(i).equals(wanna)) {

return i;

}

}

return -1;

}

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

// TODO a TODO a TODO

BufferedReader f=new BufferedReader(new FileReader("lake.9.in"));

PrintWriter pw=new PrintWriter(new BufferedWriter(new FileWriter("lake.out")));

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

//throw new Exception("Not finished");

int x=Integer.parseInt(st.nextToken())+1;int y=Integer.parseInt(st.nextToken())+1;int z=Integer.parseInt(st.nextToken());

ArrayList<int[]> al=new ArrayList<int[]>();

int[] build= {0,0};

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

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

build[0]=Integer.parseInt(st.nextToken());

build[1]=Integer.parseInt(st.nextToken());

al.add(build.clone());

}

int[][] map=new int[x][y];

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

build=al.get(i);

map[build[0]][build[1]]=1;

}

int[][] logic={{1,0},{-1,0},{0,1},{0,-1}};

Stack<Integer> X=new Stack<Integer>();Stack<Integer> Y=new Stack<Integer>();

int answer=-1;

int RAM=0;

while(!(al.isEmpty())) {

//System.out.println("DEBUG:"+x+" "+y+" "+z);

RAM=0;

X.clear();

Y.clear();

build=al.remove(0);

X.add(build[0]);

Y.add(build[1]);

while(!(X.isEmpty())) {

//System.out.println("DEBUG2:"+x+" "+y+" "+z);

x=X.pop();

y=Y.pop();

try {

if(map[x][y]==1) {

map[x][y]=-2;

for(int j=0;j<logic.length;j++) {

build=logic[j];

X.push(x+build[0]);

Y.push(y+build[1]);

}

RAM++;

}

}catch(Exception e) {

//e.printStackTrace();

//System.out.println("INFO:OUT OF BOUNDS");

}

/*

new ProcessBuilder("cmd", "/c", "cls").inheritIO().start().waitFor();

for(int i=0;i<map.length;i++) {

for(int j=0;j<map[0].length;j++) {

System.out.print(map[i][j]+" ");

}

System.out.println();

}

//Thread.sleep(2000);

*

*/

}

if(RAM>answer) {

answer=RAM;

}

}

System.out.println(answer);

}

}