#include <bits/stdc++.h>

#define int long long
#define ll long long
#define ld long double
#define endl '\n'
#define st first
#define nd second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
using namespace std;
int inf=1000000007;
ll infl=1000000000000000007;
int mod=1000000007;
int mod1=998244353;

const int N=307;

int r,c,n;
int ans=inf;

int x[N],y[N];

void check(int U,int D)
{
    set<pair<int,int>>X;
    vector<pair<int,int>>E;
    int S=0,L=0,R=0;
    for(int i=1;i<=n;i++)
    {
        if(max(1,x[i]-D)==1) X.insert({y[i],i});
        else E.pb({max(1,x[i]-D),-i});
        if(min(r,x[i]+U)<r) E.pb({min(r,x[i]+U)+1,i});
    }
    if(sz(X)==0) return ;
    R=(*X.begin()).st-1;
    L=c-(*--X.end()).st;
    int last=-1;
    for(auto [Y,i]:X)
    {
        if(last!=-1) S=max(S,Y-last-1);
        last=Y;
    }
    X.insert({-inf,0});
    X.insert({inf,0});
    sort(all(E));
    for(auto [t,i]:E)
    {
        if(i<0) X.insert({y[-i],-i});
        else
        {
            X.erase({y[i],i});
            if(sz(X)==2) return ;
            int LL=(*--X.upper_bound({y[i],0})).st;
            int RR=(*X.upper_bound({y[i],0})).st;
            if(LL==-inf) R=max(R,RR-1);
            if(RR==inf) L=max(L,c-LL);
            if(LL!=-inf&&RR!=inf) S=max(S,RR-LL-1);
        }
    }
    ans=min(ans,U+D+max(S,R+L));
}

signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin>>r>>c>>n;
    for(int i=1;i<=n;i++) cin>>x[i]>>y[i];
    set<int>cnd;
    cnd.insert(0);
    for(int i=1;i<=n;i++)
    {
        cnd.insert(x[i]-1);
        cnd.insert(r-x[i]);
        for(int j=1;j<=n;j++) cnd.insert(abs(x[i]-x[j])-1);
    }
    for(auto i:cnd) for(auto j:cnd) check(i,j);
    cout<<ans;




    return 0;
}
/*
4 4
4
1 1
1 4
4 1
4 4
*/