#include <map>
#include <set>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <bitset>
#include <cctype>
#include <cstdio>
#include <limits>
#include <string>
#include <vector>
#include <cassert>
#include <climits>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <iomanip>
#include <numeric>
#include <sstream>
#include <utility>
#include <iostream>
#include <algorithm>
#include <functional>

#define stop exit(0)
#define nc -1
#define eps 1e-10
#define inf 1000000000
#define mod 1000000007
#define mp make_pair
#define MAXN 100100

#define fill(array,value) memset(array,value,sizeof(array))
#define f(i,beg,end) for(int i=beg; i<=end; i++)
#define F(i,beg,end) for(int i=beg; i>=end; i--)
#define Max(a,b) ( (a>b)?a:b )
#define Min(a,b) ( (a<b)?a:b )
#define pi 3.1415926535897932384626433832
#define iread(var) scanf("%d",&var)
#define dread(var) scanf("%f",&var)
#define lread(var) scanf("%lld",&var)
#define input(name) freopen(name,"r",stdin)
#define output(name) freopen(name,"w",stdout)
typedef unsigned long long ull;
typedef unsigned int ui;
typedef long double ld;
typedef long long ll;

using namespace std;

struct point
{
    double x, y;
    point(double xx=-100, double yy=-100)
    {
        x = xx;
        y = yy;
    }
};
double myDistance(point a, point b)
{
//    return (a.x - b.x)*(a.x - b.x) + (a.y - b.y)*(a.y - b.y);
    double ret = max( fabs(a.x-b.x), fabs(a.y-b.y));
    return ret;
//    return fabs(a.x-b.x) + fabs(a.y+b.y);
}

bool operator==(const point &a, const point &oo)
{
    return a.x==oo.x && a.y==oo.y;
}

#define EPS 1E-10

const point LOW_POINT(-1,-1);
const point HIGH_POINT(1000000001, 1000000001);
const pair <point,point> NOT_FOUND = make_pair(LOW_POINT,HIGH_POINT);

int n;
point p[MAXN];

bool xcmp(point a, point b)
{
    return a.x < b.x;
}

bool ycmp(int a, int b)
{
    return p[a].y < p[b].y;
}

pair < point, point > cpsolve(int a[MAXN], int L, int R)
{
    int i, j, k, n = R-L, mid = (L+R)>>1;
    if (n<=1) return NOT_FOUND;
    if (n==2) return mp(p[a[0]],p[a[1]]);

    int b[MAXN];
    for(i = k = 0, j = mid - L; k < n; k++)
        if(a[k] <= mid && i < (mid-L))
            b[i++] = a[k];
        else
            b[j++] = a[k];

    pair < point, point > ans,
                          a1 = cpsolve(b,L,mid),
                          b1 = cpsolve(b+mid-L, mid+1, R);

    if (myDistance(a1.first,a1.second) < myDistance(b1.first,b1.second))
    {
        ans = a1;
    }
    else
    {
        ans = b1;
    }

    /* combine */
    int f[MAXN], t = 0;
    for(k = 0; k < n; k++)
        if(fabs(p[a[k]].x - p[mid].x) - myDistance(ans.first,ans.second) < EPS)
            f[t++] = a[k];

    for(i = 0; i < t-1; i++) {
        for(j = min(i+7, t-1); j > i; j--) {
            double d = myDistance(p[f[i]], p[f[j]]);
            if(d < myDistance(ans.first,ans.second)) ans = mp(p[f[i]], p[f[j]]);
        }
    }
    return ans;
}
pair < point, point > closestpair()
{
    int a[MAXN];
    f(i,0,n-1)
        a[i] = i;
    sort(p, p+n, xcmp);
    sort(a, a+n, ycmp);
    return cpsolve(a, 0, n);
}

int main()
{
//    input("test.txt");
    input("robot.in");
    output("robot.out");

    int jj1, jj2;
    scanf("%d%d%d", &jj1, &jj2, &n);
    {
        f(i,0,n-1)
            scanf("%lf %lf", &p[i].x, &p[i].y);

        pair <point, point> ans = (closestpair());

        if(ans == NOT_FOUND)
        {
            printf("Something went terribly wrong...\n");
        }
        else
        {
            int answ = myDistance(ans.first,ans.second);
            printf("%d\n",answ);
//            cout << ans.first.x << " " << ans.first.y << " -- " << ans.second.x << " " << ans.second.y << endl;
        }
    }
    return 0;
}