#include <bits/stdc++.h>
using namespace std;
#define int long long
#define double long double
#define FOR(i,l,r,d) for(int i=(l);i<=(r);i+=(d))
#define szof(x) ((int)(x).size())
#define vi vector<int>
#define pii pair<int,int>
#define F first
#define S second
#define pb push_back
#define eb emplace_back
#define mkp make_pair
const int INF = 2147483647;
const int LNF = 1e18;
const int MOD = 1000000007;
const int mod = 998244353;
const double eps = 1e-12;
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("unroll-loops")
const int MAX = 310;
int n;
int R, C;
pii pt[MAX];
int res;
int check(int dxl, int dxr){
//cerr<<"check("<<dxl<<", "<<dxr<<") : "<<endl;
multiset<int> st;
vector<vi> ev;
/// insert : time, 1, pos
/// erase : time, -1, pos
vector<vi> seg; /// minL, minR, minSum, L, R
FOR(i, 1, n, 1){
ev.pb({pt[i].F - dxl, 1, pt[i].S});
ev.pb({pt[i].F + dxr + 1, -1, pt[i].S});
}
sort(ev.begin(), ev.end());
int pv_time = -LNF;
int minL = LNF, minR = LNF, minSum = LNF;
for(auto E : ev){
int Time = E[0];
int type = E[1];
int pos = E[2];
if(pv_time < Time){
seg.pb({minL, minR, minSum, pv_time, Time - 1});
}
pv_time = Time;
if(type == 1){
st.insert(pos);
}
else{
auto it = st.find(pos);
st.erase(it);
}
if(st.empty()){
minSum = LNF;
}
else{
minSum = 0;
for(auto it=st.begin(); it!=st.end(); it++){
if(it == st.begin()){
minL = *it - 1;
}
if(next(it) == st.end()){
minR = C - *it;
}
else{
auto nit = next(it);
minSum = max(minSum, *nit - *it - 1);
}
}
}
}
int retL = 0, retR = 0, retSum = 0;
//cerr<<"seg : "<<endl;
bool AC = 0;
for(auto I : seg){
if(I[3] > R or I[4] < 1){
continue;
}
/*
cerr<<"{";
for(auto i : I){
cerr<<i<<", ";
}
cerr<<"}"<<endl;
*/
retL = max(retL, I[0]);
retR = max(retR, I[1]);
retSum = max(retSum, I[2]);
if(I[4] >= R){
AC = 1;
}
}
retSum = max(retSum, retL + retR);
if(AC == 0){
retSum = LNF;
}
//cerr<<dxl + dxr + retSum<<endl;
return dxl + dxr + retSum;
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
cin>>R>>C;
cin>>n;
FOR(i, 1, n, 1){
cin>>pt[i].F>>pt[i].S;
}
res = LNF;
FOR(dxl, 0, R, 1){
FOR(dxr, 0, R, 1){
res = min(res, check(dxl, dxr));
}
}
cout<<res<<'\n';
return 0;
}
