#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;
#define ll long long
#define v vector
#define lp(i, s, e) for (int i = s; i < e; ++i)
struct P {
ll x, y;
bool operator<(const P &o) const {
if (x != o.x)
return x < o.x;
return y < o.y;
}
};
ll R_grid, C_grid;
int N;
v<P> pts;
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> R_grid >> C_grid >> N;
pts.resize(N);
lp(i, 0, N) { cin >> pts[i].x >> pts[i].y; }
sort(pts.begin(), pts.end());
v<ll> h_cands;
lp(i, 0, N) {
lp(j, i, N) { h_cands.push_back(pts[j].x - pts[i].x); }
}
sort(h_cands.begin(), h_cands.end());
h_cands.erase(unique(h_cands.begin(), h_cands.end()), h_cands.end());
ll ans = 4e18;
lp(hi, 0, h_cands.size()) {
ll H = h_cands[hi];
ll max_gap = 0;
lp(i, 1, N) { max_gap = max(max_gap, pts[i].x - pts[i - 1].x - 1); }
if (max_gap > H)
continue;
ll L_req = 0, R_req = 0, W_req = 0;
lp(i, 0, N) {
ll min_y = 4e18, max_y = -4e18;
bool found = false;
lp(j, 0, N) {
if (pts[j].x >= pts[i].x && pts[j].x <= pts[i].x + H) {
min_y = min(min_y, pts[j].y);
max_y = max(max_y, pts[j].y);
found = true;
}
}
if (found) {
L_req = max(L_req, min_y - 1);
R_req = max(R_req, C_grid - max_y);
}
}
ll cur = max(L_req + R_req, W_req);
ans = min(ans, H + cur);
}
cout << ans << "\n";
return 0;
}
