#include<bits/stdc++.h>
using namespace std;
#define pii pair<int,int>
#define X first
#define Y second
const int maxn = 300 + 5;
const int inf = 1e9;
int n,R,C;
pii p[maxn];
vector<int> forup, fordown;
int sz;
map<int,int> mp;
vector<int> have[maxn*2];
int main() {
// freopen("try.txt","w",stdout);
scanf("%d%d%d",&R,&C,&n);
for(int i=1;i<=n;i++) scanf("%d%d",&p[i].X,&p[i].Y);
int ans = inf;
for(int i=1;i<=n;i++) forup.push_back(p[i].X-1), fordown.push_back(R-p[i].X);
sort(forup.begin(),forup.end());
sort(fordown.begin(),fordown.end());
forup.erase(unique(forup.begin(),forup.end()),forup.end());
fordown.erase(unique(fordown.begin(),fordown.end()),fordown.end());
sort(&p[1],&p[n+1]);
for(auto up : forup) {
for(auto down : fordown) {
mp.clear(); sz = 0;
for(int x=1;x<=n;x++) {
mp[max(1,p[x].X-up)];
mp[min(R,p[x].X+down)+1];
}
for(auto &t : mp) t.second = ++sz;
for(int i=1;i<=sz;i++) have[i].clear();
for(int x=1;x<=n;x++) {
for(int i=mp[max(1,p[x].X-up)];i<=mp[min(R,p[x].X+down)+1]-1;i++) {
have[i].push_back(p[x].Y);
}
}
for(int row=1;row<=sz;row++) if(have[row].size()>0) sort(have[row].begin(), have[row].end());
int left = 0, right = 0, gap = 0;
for(int row=1;row<=sz;row++) {
if(have[row].size()==0) continue;
// printf("\trow = %d : ",rec[row]);
// for(auto x : have[row]) printf("%d ",x);
// printf("\n");
left = max(left, *have[row].begin()-1);
right = max(right, C-*have[row].rbegin());
}
for(int row=1;row<=sz;row++) {
for(int i=1;i<have[row].size();i++) gap = max(gap, have[row][i]-have[row][i-1]-1-left-right);
}
int gaprow = 0;
for(int i=2;i<=n;i++) gaprow = max(gaprow, p[i].X-p[i-1].X-1-up-down);
ans = min(ans, up + down + left + right + gap + gaprow);
// printf("up = %d down = %d (%d) : use %d %d %d\n",up,down,gaprow,left,right,gap);
}
}
printf("%d",ans);
}
