#ifdef _WIN32
#  define LL "%I64d"
#else
#  define LL "%Ld"
#endif

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>
#include <ctime>
#include <vector>
#include <deque>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <bitset>
#include <string>
#include <algorithm>
#include <complex>
#include <utility>
#include <cassert>
using namespace std;
#define null NULL
#define mp make_pair
#define pb(a) push_back(a)
#define sz(a) ((int)(a).size())
#define all(a) a.begin() , a.end()
#define fi first
#define se second
#define relaxMin(a , b) (a) = min((a),(b))
#define relaxMax(a , b) (a) = max((a),(b))
#define SQR(a) ((a)*(a))
typedef vector<int> vi;
typedef pair<int,int> pii;
typedef long long ll;
// Bit
#define MAX 100010
int sum[MAX];
void add(int pos , int how){
  ++pos;
  for(;pos < MAX; pos += pos&(-pos))
   sum[pos] += how;
}
int get(int fr , int to){
  ++fr , ++to;
  int ret = 0;
  for(;to>0;to -= to&(-to))
   ret += sum[to];
  --fr;
  for(;fr>0;fr -= fr&(-fr))
   ret -= sum[fr];
  return ret;
}
// end
int N , M , K;
vector<pii> pts;
vi Y;
int up(int pos , int dlt){
  return lower_bound(all(Y) , pos + dlt + 1) - Y.begin() - 1;
}
int down(int pos , int dlt){
  return lower_bound(all(Y) , pos - dlt) - Y.begin();
}
bool can(int how){
  memset(sum , 0 , sizeof sum);
  int Last = 0;
  for(int i=0;i<sz(pts);++i){
   while(pts[i].fi - pts[Last].fi > how){
    add(down(pts[Last].se , 0) , -1);
    ++Last;
                                        }
   if(get(down(pts[i].se , how) , up(pts[i].se , how)) > 0)
    return true;
   add(down(pts[i].se , 0) , +1);
                            }
  return false;
}
int main(){
  freopen("robot.in" , "r" , stdin);
  freopen("robot.out" , "w" , stdout);
  scanf("%d%d%d" , &N , &M , &K);
  //N = M = K = 100000;
  pts.resize(K);
  for(int i=0;i<sz(pts);++i){
   scanf("%d%d" , &pts[i].fi , &pts[i].se);
   //pts[i].fi = rand() , pts[i].se = rand();
   Y.pb(pts[i].se);
                            }
  sort(all(pts));
  sort(all(Y));
  Y.erase(unique(all(Y)) , Y.end());
  ll lo = 0 , hi = 1000000001 , mid;
  for(;;){
   if(lo+1 >= hi){
    if(can(lo)) mid = lo;
    else mid = hi;
    break;
                 }
   mid = (lo+hi)>>1;
   if(can(mid)) hi = mid;
   else lo = mid;
         }
  cout<<mid<<'\n';
  //printf("%.3lf\n" , (clock() - 0.0)/CLOCKS_PER_SEC);
  return 0;
}