#include<bits/stdc++.h>
using namespace std;
using ll = long long;
const int N=305;
const ll INF=1e18;
int n;
ll r,c;
ll x[N],y[N];
ll calc(ll xl,ll xr){
vector<ll> xs;
for(int i=0;i<n;i++){
xs.emplace_back(max(1LL,x[i]-xl));
xs.emplace_back(min(r,x[i]+xr));
xs.emplace_back(max(1LL,x[i]-xl-1));
xs.emplace_back(min(r,x[i]+xr+1));
}
sort(xs.begin(),xs.end());
xs.erase(unique(xs.begin(),xs.end()),xs.end());
int xn=xs.size();
vector<vector<pair<ll,int>>> event(xn);
for(int i=0;i<n;i++){
int xi=lower_bound(xs.begin(),xs.end(),max(1LL,x[i]-xl))-xs.begin();
int xj=upper_bound(xs.begin(),xs.end(),min(r,x[i]+xr))-xs.begin();
event[xi].emplace_back(y[i],1);
if(xj<xn){
event[xj].emplace_back(y[i],0);
}
}
ll mxa=0,mxb=0,sum=0;
multiset<ll> pts,dif;
for(auto &e:event){
for(auto [x,t]:e){
if(t){
auto it=pts.emplace(x);
if(next(it)!=pts.end()&&it!=pts.begin()){
dif.erase(dif.find(*next(it)-*prev(it)));
}
if(next(it)!=pts.end()){
dif.emplace(*next(it)-*it);
}
if(it!=pts.begin()){
dif.emplace(*it-*prev(it));
}
}else{
auto it=pts.find(x);
assert(it!=pts.end());
if(next(it)!=pts.end()){
dif.erase(dif.find(*next(it)-*it));
}
if(it!=pts.begin()){
dif.erase(dif.find(*it-*prev(it)));
}
if(next(it)!=pts.end()&&it!=pts.begin()){
dif.emplace(*next(it)-*prev(it));
}
pts.erase(it);
}
}
if(pts.empty())return INF;
mxa=max(mxa,*pts.begin()-1);
mxb=max(mxb,c-*pts.rbegin());
if(!dif.empty()){
sum=max(sum,*dif.rbegin()-1);
}
}
return xl+xr+max(sum,mxa+mxb);
}
int main(){
cin.tie(nullptr)->sync_with_stdio(false);
cin >> r >> c >> n;
for(int i=0;i<n;i++){
cin >> x[i] >> y[i];
}
vector<ll> xs;
for(int i=0;i<n;i++){
xs.emplace_back(x[i]-1);
xs.emplace_back(r-x[i]);
for(int j=0;j<n;j++){
ll dx=abs(x[i]-x[j])-1;
if(dx>=0)xs.emplace_back(dx);
}
}
assert(xs.size()>=r-1);
sort(xs.begin(),xs.end());
xs.erase(unique(xs.begin(),xs.end()),xs.end());
ll ans=INF;
for(int xl:xs){
for(int xr:xs){
ans=min(ans,calc(xl,xr));
}
}
cout << ans;
}
