#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
void openFiles() {
#ifdef KEK
assert(freopen("input.txt", "r", stdin));
assert(freopen("output.txt", "w", stdout));
#endif
}
void IOoptimize() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
}
struct Action {
int time;
int l, r;
int type;
int id;
};
bool operator< (const Action &a1, const Action &a2) {
if (a1.time == a2.time)
return a1.id < a2.id;
return a1.time < a2.time;
}
struct Segment {
int val;
int cnt;
int add;
Segment() {}
Segment(int val, int cnt, int add) : val(val), cnt(cnt), add(add) {}
};
const int MAXN = 300;
const int MAX = 40;
int x[MAXN], y[MAXN];
Segment t[5 * MAX];
Segment merge(const Segment &s1, const Segment &s2) {
if (s1.val < s2.val)
return s1;
if (s2.val < s1.val)
return s2;
Segment s3;
s3.add = 0;
s3.val = s1.val;
s3.cnt = s1.cnt + s2.cnt;
return s3;
}
void push(int x, int l, int r) {
t[x].val += t[x].add;
if (r - l > 1) {
t[2 * x + 1].add += t[x].add;
t[2 * x + 2].add += t[x].add;
}
t[x].add = 0;
}
void update(int x, int l, int r, int ql, int qr, int val) {
push(x, l, r);
if (l >= qr || r <= ql)
return;
if (ql <= l && r <= qr) {
t[x].add += val;
push(x, l, r);
return;
}
int c = (l + r) / 2;
update(2 * x + 1, l, c, ql, qr, val);
update(2 * x + 2, c, r, ql, qr, val);
t[x] = merge(t[2 * x + 1], t[2 * x + 2]);
}
Segment query(int x, int l, int r, int ql, int qr) {
push(x, l, r);
if (l >= qr || r <= ql)
return Segment(INT_MAX, 0, 0);
if (ql <= l && r <= qr)
return t[x];
int c = (l + r) / 2;
return merge(
query(2 * x + 1, l, c, ql, qr),
query(2 * x + 2, c, r, ql, qr)
);
}
int main() {
openFiles();
IOoptimize();
int r, c;
cin >> r >> c;
int n;
cin >> n;
for (int i = 0; i < n; i++) {
cin >> x[i] >> y[i];
x[i]--;
y[i]--;
}
int ans = INT_MAX;
int cnt[4];
for (cnt[0] = 0; cnt[0] <= MAX; cnt[0]++)
for (cnt[1] = 0; cnt[1] <= MAX; cnt[1]++)
for (cnt[2] = 0; cnt[2] <= MAX; cnt[2]++)
for (cnt[3] = 0; cnt[3] <= MAX; cnt[3]++) {
int new_ans = cnt[0] + cnt[1] + cnt[2] + cnt[3];
if (ans <= new_ans)
continue;
vector<Action> v;
for (int i = 0; i < n; i++) {
Action act;
act.id = i;
act.time = max(y[i] - cnt[1], 0);
act.l = max(x[i] - cnt[0], 0);
act.r = min(x[i] + cnt[2], r - 1);
act.type = 1;
v.push_back(act);
act.time = min(y[i] + cnt[3] + 1, c);
act.type = -1;
v.push_back(act);
}
sort(v.begin(), v.end());
for (int i = 0; i < 5 * MAX; i++) {
t[i].val = 0;
t[i].cnt = 1;
t[i].add = 0;
}
int last = 0;
int sq = 0;
for (auto act : v) {
//cout << act.time << " " << act.l << " " << act.r << " " << act.type << "\n";
int active_count = 0;
Segment seg = query(0, 0, r, 0, r);
if (seg.val == 0) {
active_count = r - seg.cnt;
}
else {
active_count = r;
}
sq += active_count * (act.time - last);
last = act.time;
update(0, 0, r, act.l, act.r + 1, act.type);
}
//cout << sq << "\n";
//cout << "--/--\n";
if (sq == r * c)
ans = new_ans;
}
cout << ans;
return 0;
}
