#include<bits/stdc++.h>
using namespace std;
int N, R, C, x[309], y[309], precalc[309][309][3];
const int INF = 1e9 + 100;
unsigned int ans = UINT_MAX;
set < int > sa, sb, sab;
namespace ds {
multiset < int > xs, dx;
void init ()
{
xs.clear (), dx.clear ();
}
void delDif (int x)
{
dx.erase (dx.find (x));
}
void add (int x)
{
if (xs.find (x) != xs.end ()) xs.insert (x);
else
{
xs.insert (x);
auto it1 = xs.lower_bound (x), it2 = xs.upper_bound (x);
if (it1 != xs.begin () && it2 != xs.end ())
it1 --,
delDif ((*it2) - (*it1)),
it1 ++;
if (it1 != xs.begin ())
it1 --,
dx.insert (x - (*it1));
if (it2 != xs.end ())
dx.insert ((*it2) - x);
}
}
void del (int x)
{
if (xs.count (x) >= 2) xs.erase (xs.find (x));
else
{
auto it1 = xs.lower_bound (x), it2 = xs.upper_bound (x);
if (it1 != xs.begin () && it2 != xs.end ())
it1 --,
dx.insert ((*it2) - (*it1)),
it1 ++;
if (it1 != xs.begin ())
it1 --,
delDif (x - (*it1));
if (it2 != xs.end ())
delDif ((*it2) - x);
xs.erase (x);
}
}
int maxDif ()
{
if (dx.empty ()) return 0;
return *(dx.rbegin ());
}
int getA ()
{
if (xs.empty ()) return INF;
return (*xs.begin ()) - 1;
}
int getB ()
{
if (xs.empty ()) return INF;
return C - (*xs.rbegin ());
}
void store (int &a, int &b, int &df)
{
a = getA ();
b = getB ();
df = maxDif () - 1;
}
};
unsigned int pos[1209];
int nr, stat[1209][3];
int dq[3][1209], fst[3], lst[3];
void clearDeque ()
{
for (int i=0; i<3; i++)
fst[i] = 1, lst[i] = 0;
}
void add (int pos)
{
for (int i=0; i<3; i++)
{
while (fst[i] <= lst[i] && stat[dq[i][lst[i]]][i] <= stat[pos][i])
lst[i] --;
dq[i][++lst[i]] = pos;
}
}
void del (int pos)
{
for (int i=0; i<3; i++)
while (fst[i] <= lst[i] && dq[i][fst[i]] <= pos)
fst[i] ++;
}
int getSum ()
{
if (fst[0] > lst[0]) return 2 * INF;
int minA = stat[dq[0][fst[0]]][0], minB = stat[dq[1][fst[1]]][1], minAB = stat[dq[2][fst[2]]][2];
return max (minA + minB, minAB);
}
unsigned int relevantXs[609], relevantX1[309], relevantX2[309];
unsigned int relevantShifts[1209], relevantS1[609], relevantS2[609];
void solve (int updown)
{
ds::init ();
clearDeque ();
for (int i=1; i<=N; i++)
relevantX2[i] = x[i] + updown + 1;
merge (relevantX1 + 1, relevantX1 + N + 1, relevantX2 + 1, relevantX2 + N + 1, relevantXs + 1);
nr = 1, pos[1] = -0, stat[1][0] = INF, stat[1][1] = INF, stat[1][2] = -1;
int l = 1, r = 0;
for (int currPos = 1; currPos <= 2 * N; currPos ++)
{
unsigned int t = relevantXs[currPos];
while (r < N && x[r + 1] <= t)
r ++;
while (x[l] + updown < t && l <= N)
l ++;
nr ++, pos[nr] = t;
stat[nr][0] = precalc[l][r][0];
stat[nr][1] = precalc[l][r][1];
stat[nr][2] = precalc[l][r][2];
}
pos[nr + 1] = UINT_MAX;
int n = 0, m = 0, p = 0;
for (int i=1; i<=nr; i++)
{
if (i > 1 && pos[i] - 1 <= updown)
relevantS1[++n] = pos[i] - 1;
if (pos[i] >= R && pos[i] - R <= updown)
relevantS2[++m] = pos[i] - R;
}
merge (relevantS1 + 1, relevantS1 + n + 1, relevantS2 + 1, relevantS2 + m + 1, relevantShifts + 1);
p = n + m, relevantShifts[++p] = updown;
int j = 1, i = 1;
for (int currPos = 1; currPos <= p; currPos ++)
if (currPos == 1 || relevantShifts[currPos] != relevantShifts[currPos - 1])
{
unsigned int shift = relevantShifts[currPos];
while (j <= nr && pos[j] <= R + shift)
add (j), j++;
while (pos[i + 1] - 1 < 1 + shift)
del (i), i ++;
unsigned int curr = updown + getSum ();
if (curr < ans)
ans = curr;
}
}
void readAndSort ()
{
pair < int, int > point[309];
scanf ("%d %d\n", &R, &C);
scanf ("%d", &N);
for (int i=1; i<=N; i++)
scanf ("%d %d", &point[i].first, &point[i].second);
sort (point + 1, point + N + 1);
for (int i=1; i<=N; i++)
x[i] = point[i].first, y[i] = point[i].second;
}
void doPrecalc ()
{
for (int i=1; i<=N + 1; i++)
{
ds::init ();
ds::store (precalc[i][i - 1][0], precalc[i][i - 1][1], precalc[i][i - 1][2]);
for (int j=i; j<=N; j++)
ds::add (y[j]),
ds::store (precalc[i][j][0], precalc[i][j][1], precalc[i][j][2]);
}
}
int main ()
{
//freopen ("input", "r", stdin);
//freopen ("output", "w", stdout);
readAndSort ();
doPrecalc ();
for (int i=1; i<=N; i++)
sa.insert (x[i] - 1), sb.insert (R - x[i]), relevantX1[i] = x[i];
for (int i=1; i<=N; i++)
for (int j=i + 1; j<=N; j++)
if (x[i] != x[j])
{
int val = x[i] - x[j];
if (val < 0) val = -val;
sab.insert (val - 1);
}
for (auto a : sa)
for (auto b : sb)
sab.insert (a + b);
for (auto ab : sab)
{
if (ans >= ab)
solve (ab);
}
printf ("%d\n", ans);
return 0;
}
