#include <cstdio>

#include <string>

#include <cstdlib>

#include <cmath>

#include <iostream>

#include <cstring>

#include <set>

#include <queue>

#include <algorithm>

#include <vector>

#include <map>

#include <cctype>

using namespace std ;

typedef long long LL;

typedef pair<int, int> P;

const int INF = 0x3f3f3f3f;

const double inf = 0x3f3f3f3f3f3f3f;

const double eps = 1e-8;

const int maxn = 1e4 + 5;

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

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

int n, m;

inline bool is_in(int r, int c){

    return r >= 0 && r < n && c >= 0 && c < m;

}

int a[30];

int ans;

bool isly(int x){

    int b[] = { x+1, x-1, x+m, x-m};

    int d[] = { x/m*m+m-1, x/m*m, n-1, 0};

    int c[] = { 1, -1, m, -m};

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

        bool ok = false;

        for(int j = b[i]; (i & 1 ? j >= d[i] : j <= d[i]); j += c[i]){

            if(ok && a[j] != -1){

                if(a[j] == 1)  return false;

                else break;

            }

            else if(!ok && a[j] != -1) ok = true;

        }

    }

    return true;

}

void dfs(int x, int cnt){

    ans = max(ans, cnt);

    for(int i = x; i < n; ++i){

        if(a[i] != -1 || !isly(i))  continue;

        a[i] = 1;

        dfs(i+1, cnt+1);

        a[i] = -1;

    }

}

int main(){

    int c;

    while(scanf("%d %d %d", &n, &m, &c) == 3){

        n *= m;

        memset(a, -1, sizeof(a));

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

            int x, y;

            scanf("%d %d", &x, &y);

            a[x*m+y] = 0;

        }

        ans = 0;

        dfs(0, 0);

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

    }

    return 0;

}