#include <bits/stdc++.h>
using namespace std;
int main() {
int n, x0, y0;
cin >> x0 >> y0 >> n;
int a[n], b[n];
for(int i=0;i<n;i++) {
cin >> a[i] >> b[i];
a[i]--;
b[i]--;
}
int ans = 2e9;
for(int west=0;west<x0;west++)
for(int east=0;east<x0;east++)
for(int north=0;north<y0;north++)
for(int south=0;south<y0;south++) {
int gr[x0+1][y0+1];
memset(gr,0,sizeof(gr));
for(int i=0;i<n;i++) {
gr[max(a[i]-west,0)][max(b[i]-south,0)]++;
gr[max(a[i]-west,0)][min(b[i]+north+1,y0)]--;
gr[min(a[i]+east+1,x0)][max(b[i]-south,0)]--;
gr[min(a[i]+east+1,x0)][min(b[i]+north+1,y0)]++;
}
for(int i=0;i<x0;i++)
for(int j=0;j<y0-1;j++)
gr[i][j+1]+=gr[i][j];
for(int i=0;i<x0-1;i++)
for(int j=0;j<y0;j++)
gr[i+1][j]+=gr[i][j];
bool val = 1;
for(int i=0;i<x0;i++)
for(int j=0;j<y0;j++)
if(!gr[i][j])
val = 0;
if(val)
ans = min(ans, north+south+east+west);
}
cout << ans;
}
