#include "bits/stdc++.h"
using namespace std;
#define ar array
typedef long long ll;
#define int ll
signed main(){
ios::sync_with_stdio(0); cin.tie(0);
int n, m; cin >> n >> m;
int sz; cin >> sz;
vector<int> x(sz), y(sz);
for(int i=0;i<sz;i++){
cin >> x[i] >> y[i];
}
vector<int> p(sz);
iota(p.begin(), p.end(), 0);
sort(p.begin(), p.end(), [&](int i, int j){
return y[i] < y[j];
});
int res = 2 * (n + m);
for(int u=0;u<n;u++){
for(int d=0;d<n;d++){
vector<vector<int>> used(n + 1);
for(auto i : p){
int l = max(1ll, x[i] - u), r = min(n, x[i] + d);
for(int j=l;j<=r;j++){
used[j].push_back(y[i]);
}
}
int mnl = 0, mnr = 0, mn = 0, ok = 1;
for(int i=1;i<=n;i++){
if(used[i].empty()){
ok = 0;
break;
}
mnl = max(mnl, used[i][0] - 1);
mnr = max(mnr, m - used[i].back());
for(int j=1;j<(int)used[i].size();j++){
//~ cout<<i<<" "<<used[i][j]<<" "<<used[i][j-1]<<"\n";
mn = max(mn, used[i][j] - used[i][j-1] - 1);
}
}
if(!ok) continue;
//~ cout<<u<<" "<<d<<" "<<mnl<<" "<<mnr<<" "<<mn<<"\n";
res = min(res, u + d + max(mnl + mnr, mn));
}
}
cout<<res<<"\n";
}
