#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
#define int ll
#define all int i=0; i<n; i++
#define pb push_back
#define pf push_front

#define FAST_IO ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL)

int n;
vector< pair<int, int> >v;
map<pair<int, int> , int> cult;
map<pair<int, int> , int> vertex;
map<int, pair<int, int> >inv;
vector<int>g[100005];
int visit[100005];
int ans = 0;
int k = 0;

void dfs(int source){
    visit[source] = 1;
    int x = inv[source].first; int y = inv[source]. second;
    if(cult[{x+1, y}] == 0)k++;

    if(cult[{x, y+1}] == 0)k++;

    if(cult[{x, y-1}] == 0)k++;

    if(cult[{x-1, y}] == 0)k++;

    for(int j=0; j<g[source].size(); j++){
        if(visit[g[source][j]]==0){
            dfs(g[source][j]);
        }
    }
}



int32_t main()
{
    FAST_IO;
    int r,c,n;
    cin>>r>>c>>n;
    int a,b;

    for(int i=0; i<n; i++){
        visit[i] = 0;
        cin>>a>>b;
        cult[{a-1, b-1}] = 1;
        vertex[{a-1, b-1}] = i;
        inv[i] = {a-1, b-1};
        v.pb({a-1, b-1});
    }

    for(int i=0; i<n; i++){
        int x = v[i].first;
        int y = v[i].second;

        if(cult[{x+1, y}] == 1)g[vertex[{x,y}]].pb(vertex[{x+1, y}]);

        if(cult[{x, y+1}] == 1)g[vertex[{x,y}]].pb(vertex[{x, y+1}]);

        if(cult[{x, y-1}] == 1)g[vertex[{x,y}]].pb(vertex[{x, y-1}]);

        if(cult[{x-1, y}] == 1)g[vertex[{x,y}]].pb(vertex[{x-1, y}]);
    }

    for(int i=0; i<n; i++){
        if(visit[i]==0){
            //cout<<"dfs initiated at source"<<" "<<i<<endl;
            k=0;
            dfs(i);
        }
        ans = max(k, ans);
    }

    cout<<ans<<endl;
}