#include <iostream>

 #include<cstdio>

 #include<cstring>

 #include<algorithm>

 #include<stdlib.h>

 using namespace std;

 #define N 5010

 bool flag[N][N];

 struct node

 {

     int x,y;

 }p[N];

 bool cmp(node a,node b)

 {

     if(a.x==b.x)

     return a.y<b.y;

     return a.x<b.x;

 }

 int main()

 {

     int i,j,k,n,r,c;

     while(scanf("%d%d",&r,&c)!=EOF)

     {

         memset(flag,,sizeof(flag));

         scanf("%d",&n);

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

         {

             scanf("%d%d",&p[i].x,&p[i].y);

             flag[p[i].x][p[i].y] = ;

         }

         sort(p+,p+n+,cmp);

         int ans=,ff=;

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

             for(j = i+; j <= n ; j++)

             {

                 int tx = p[j].x-p[i].x;

                 int ty = p[j].y - p[i].y;

                 int ox = p[j].x;

                 int oy = p[j].y;

                 if(p[i].x-tx>=&&p[i].x-tx<=r&&p[i].y-ty>=&&p[i].y-ty<=c)

                 continue;

                 ff = ;

                 for(k =  ; ; k++)

                 {

                     ox+=tx;

                     oy+=ty;

                     if(ox>r||oy>c||ox<||oy<)

                     break;

                     if(!flag[ox][oy])

                     {

                         ff = ;

                         break;

                     }

                 }

                 if(ff)

                 ans = max(ans,k);

             }

         if(ans>)

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

         else

         printf("0\n");

     }

     return ;

 }