#include "bits/stdc++.h"
using namespace std;
#define ar array
signed main(){
ios::sync_with_stdio(0); cin.tie(0);
int R, C; cin>>R>>C;
int n; cin>>n;
vector<int> x(n), y(n);
for(int i=0;i<n;i++){
cin>>x[i]>>y[i];
}
int res = R + C;
auto check = [&](int a, int c){
vector<vector<int>> row(R + 1);
for(int i=0;i<n;i++){
//~ x[i] - a, x[i] + c
int l = max(1, x[i] - a), r = min(R, x[i] + c);
for(int j=l;j<=r;j++) row[j].push_back(y[i]);
}
int A = 0, B = 0, D = 0;
for(int i=1;i<=R;i++){
if(row[i].empty()) return;
sort(row[i].begin(), row[i].end());
for(int j=1;j<(int)row[i].size();j++){
D = max(D, row[i][j] - row[i][j-1] - 1);
}
A = max(A, row[i][0] - 1);
B = max(B, C - row[i].back());
}
res = min(res, a + c + max(A + B, D));
};
for(int a=0;a<R;a++){
for(int c=0;a+c<R;c++){
check(a, c);
}
}
cout<<res<<"\n";
}
