#define  _CRT_SECURE_NO_WARNINGS

#include<stdio.h>

#include<string.h>

#include<math.h>

#include<algorithm>

#include<queue>

using namespace std;

#define MAXN 110

int map[MAXN][MAXN];

int n,m,sum,a[MAXN*MAXN],b[MAXN*MAXN];//runtime error 原来是这里小了

int xx[]={,,,-};

int yy[]={,-,,};

struct tt

{

    int x,y;

};

int bfs()

{

    int ans,maxx=;

    tt front,rear,temp;

    queue<tt>q;

    while(!q.empty())

        q.pop();

    for(int i=;i<sum;i++)

    {

        if(map[a[i]][b[i]]==)

        {

            front.x=a[i];front.y=b[i];

            q.push(front);

            map[a[i]][b[i]]=;

            ans=;

            while(!q.empty())

            {

                temp=q.front();

                q.pop();

                for(int j=;j<;j++)

                {

                    rear.x=temp.x+xx[j];

                    rear.y=temp.y+yy[j];

                    if(rear.x>&&rear.y>&&rear.x<=n&&rear.y<=m&&map[rear.x][rear.y]==)

                    {

                        q.push(rear);

                        map[rear.x][rear.y]=;

                        ans++;

                        maxx=maxx>ans? maxx:ans;

                    }

                }

            }

        }

    }

    return maxx;

}

int main()

{

    int i;

    while(scanf("%d%d%d",&n,&m,&sum)!=EOF)

    {

        memset(map,,sizeof(map));

        for(i=;i<sum;i++)

        {

            scanf("%d%d",&a[i],&b[i]);

            map[a[i]][b[i]]=;

        }

        printf("%d\n",bfs());

    }

    return ;

}