#include <bits/stdc++.h>
using namespace std;
using pii = pair<int, int>;
#define ff first
#define ss second
int A[50][50];
pii P[2500];
int R, C, N;
bool f(int a, int b, int c, int d) {
for (int i = 1; i <= R; ++i) fill(A[i], A[i] + C + 1, 0);
int cnt = 0;
for (int i = 0; i < N; ++i) {
for (int x = P[i].ff - a; x <= P[i].ff + b; ++x) {
for (int y = P[i].ss - c; y <= P[i].ss + d; ++y) {
if (x < 1 || x > R || y < 1 || y > C) continue;
cnt += A[x][y] == 0;
A[x][y] = 1;
}
}
}
return cnt == R * C;
}
int main() {
ios_base::sync_with_stdio(0), cin.tie(0);
cin >> R >> C >> N;
for (int i = 0; i < N; ++i) {
int x, y; cin >> x >> y;
P[i] = {x, y};
}
int ans = R + C;
for (int i = 0; i <= R; ++i) {
for (int j = 0; j <= R - i; ++j) {
for (int k = 0; k <= C; ++k) {
for (int l = 0; l <= C - k; ++l) {
if (f(i, j, k, l) && ans > i + j + k + l) ans = i + j + k + l;
}
}
}
}
cout << ans;
return 0;
}
