#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;
typedef vector<ll> vll;
const ll N = 305;
ll n, r, c, x[N], y[N], ans = 1e18;
signed main() {
ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
cin >> r >> c >> n;
for (ll i = 0; i < n; i++) cin >> x[i] >> y[i], x[i]--, y[i]--;
for (ll up = 0; up < r; up++) {
for (ll dn = 0; dn < r; dn++) {
ll mx = 0, L = 0, R = 0;
for (ll p = 0; p < r; p++) {
vll a;
for (ll i = 0; i < n; i++) if (x[i] - up <= p && x[i] + dn >= p) a.push_back(y[i]);
sort(a.begin(), a.end());
if (!a.size()) mx = 1e18;
else {
L = max(L, a[0]), R = max(R, c - a.back() - 1);
for (int i = 0; i < a.size() - 1; i++) mx = max(mx, a[i + 1] - a[i] - 1);
}
}
ans = min(ans, max(mx, L + R) + dn + up);
}
}
cout << ans;
}
