#include <bits/stdc++.h>
using namespace std;

using ll=long long;
//#define int ll

#define rng(i,a,b) for(int i=int(a);i<int(b);i++)
#define rep(i,b) rng(i,0,b)
#define gnr(i,a,b) for(int i=int(b)-1;i>=int(a);i--)
#define per(i,b) gnr(i,0,b)
#define pb push_back
#define eb emplace_back
#define a first
#define b second
#define bg begin()
#define ed end()
#define all(x) x.bg,x.ed
#ifdef LOCAL
#define dmp(x) cerr<<__LINE__<<" "<<#x<<" "<<x<<endl
#else
#define dmp(x) void(0)
#endif

template<class t,class u> void chmax(t&a,u b){if(a<b)a=b;}
template<class t,class u> void chmin(t&a,u b){if(b<a)a=b;}

template<class t> using vc=vector<t>;
template<class t> using vvc=vc<vc<t>>;

using pi=pair<int,int>;
using vi=vc<int>;

template<class t,class u>
ostream& operator<<(ostream& os,const pair<t,u>& p){
	return os<<"{"<<p.a<<","<<p.b<<"}";
}

template<class t> ostream& operator<<(ostream& os,const vc<t>& v){
	os<<"{";
	for(auto e:v)os<<e<<",";
	return os<<"}";
}

#define mp make_pair
#define mt make_tuple
#define one(x) memset(x,-1,sizeof(x))
#define zero(x) memset(x,0,sizeof(x))
#ifdef LOCAL
void dmpr(ostream&os){os<<endl;}
template<class T,class... Args>
void dmpr(ostream&os,const T&t,const Args&... args){
	os<<t<<" ";
	dmpr(os,args...);
}
#define dmp2(...) dmpr(cerr,"Line:",__LINE__,##__VA_ARGS__)
#else
#define dmp2(...) void(0)
#endif

using uint=unsigned;
using ull=unsigned long long;

template<int i,class T>
void print_tuple(ostream&,const T&){
}

template<int i,class T,class H,class ...Args>
void print_tuple(ostream&os,const T&t){
	if(i)os<<",";
	os<<get<i>(t);
	print_tuple<i+1,T,Args...>(os,t);
}

template<class ...Args>
ostream& operator<<(ostream&os,const tuple<Args...>&t){
	os<<"{";
	print_tuple<0,tuple<Args...>,Args...>(os,t);
	return os<<"}";
}

void print(ll x,int suc=1){
	cout<<x;
	if(suc==1)
		cout<<"\n";
	if(suc==2)
		cout<<" ";
}

ll read(){
	ll i;
	cin>>i;
	return i;
}

vi readvi(int n,int off=0){
	vi v(n);
	rep(i,n)v[i]=read()+off;
	return v;
}

template<class T>
void print(const vector<T>&v,int suc=1){
	rep(i,v.size())
		print(v[i],i==int(v.size())-1?suc:2);
}

string readString(){
	string s;
	cin>>s;
	return s;
}

template<class T>
T sq(const T& t){
	return t*t;
}

//#define CAPITAL
void yes(bool ex=true){
	#ifdef CAPITAL
	cout<<"YES"<<endl;
	#else
	cout<<"Yes"<<endl;
	#endif
	if(ex)exit(0);
}
void no(bool ex=true){
	#ifdef CAPITAL
	cout<<"NO"<<endl;
	#else
	cout<<"No"<<endl;
	#endif
	if(ex)exit(0);
}

constexpr ll ten(int n){
	return n==0?1:ten(n-1)*10;
}

const ll infLL=LLONG_MAX/3;

#ifdef int
const int inf=infLL;
#else
const int inf=INT_MAX/2-100;
#endif

int topbit(signed t){
	return t==0?-1:31-__builtin_clz(t);
}
int topbit(ll t){
	return t==0?-1:63-__builtin_clzll(t);
}
int botbit(signed a){
	return a==0?32:__builtin_ctz(a);
}
int botbit(ll a){
	return a==0?64:__builtin_ctzll(a);
}
int popcount(signed t){
	return __builtin_popcount(t);
}
int popcount(ll t){
	return __builtin_popcountll(t);
}
bool ispow2(int i){
	return i&&(i&-i)==i;
}
int mask(int i){
	return (int(1)<<i)-1;
}

bool inc(int a,int b,int c){
	return a<=b&&b<=c;
}

template<class t> void mkuni(vc<t>&v){
	sort(all(v));
	v.erase(unique(all(v)),v.ed);
}

ll rand_int(ll l, ll r) { //[l, r]
	#ifdef LOCAL
	static mt19937_64 gen;
	#else
    static random_device rd;
    static mt19937_64 gen(rd());
    #endif
    return uniform_int_distribution<ll>(l, r)(gen);
}

template<class t>
int lwb(const vc<t>&v,const t&a){
	return lower_bound(all(v),a)-v.bg;
}
//f(a,b) が true なら a を削除する
template<class t,class u>
struct slide{
	vc<t> x;
	vi y;
	u f;
	int b,e,c,d;
	slide(u ff=u()):f(ff){init();}
	void init(){b=e=c=d=0;}
	void push(t a){
		while(b<e&&f(x[e-1],a))e--;
		if(e==(int)x.size()){
			x.eb();
			y.eb();
		}
		x[e]=a;
		y[e++]=c++;
	}
	void pop(){if(y[b]==d)b++;d++;}
	t get(){return x[b];}
};

struct mrt{
	int l,r,z;
};

int global;

vc<mrt> tyk(int w,int h,int mx,vc<pi> xy){
	int l=0,r=w;
	vc<mrt> res;
	for(auto p:xy){
		res.pb({l,r,p.b});
		if(p.a<mx){
			chmax(l,p.a);
		}
		if(mx<=p.a){
			chmin(r,p.a);
		}
	}
	res.pb({l,r,h});
	return res;
}

int kmzk(int w,int h,int mx,int my,vc<pi> lw,vc<pi> up){
	int cut=w+h;
	if(cut<=global)return 0;
	for(auto&p:lw)p.b=my-p.b;
	reverse(all(lw));
	for(auto&p:up)p.b-=my;
	
	auto a=tyk(w,my,mx,lw);
	auto b=tyk(w,h-my,mx,up);
	
	int ans=-inf;
	
	rep(_,2){
		auto imin=[](int x,int y){return x<y;};
		int n=a.size(),m=b.size();
		slide<int,decltype(imin)> s(imin),t(imin);
		rep(i,m)t.push(b[i].r-b[i].l+b[i].z);
		int j=0,k=0;
		rep(i,n){
			while(k<m&&(b[k].l<a[i].l||a[i].r<b[k].r)){
				t.pop();
				s.push(-b[k].l+b[k].z);
				k++;
			}
			while(j<m&&b[j].l<a[i].l){
				s.pop();
				j++;
			}
			if(j<k)
				chmax(ans,a[i].r+a[i].z+s.get());
			if(k<m)
				chmax(ans,a[i].z+t.get());
		}
		swap(a,b);
	}
	
	chmax(global,ans);
	return ans;
}

int relka(int w,int h,int mx,vc<pi> xy){
	int cut=max(max(xy[0].a,w-xy[0].a)+h,max(xy[0].b,h-xy[0].b)+w);
	if(cut<=global)return 0;
	int n=xy.size();
	if(n==1){
		return cut;
	}
	
	int m=n/2;
	int my=xy[m].b;
	
	vc<pi> lw(xy.bg,xy.bg+m);
	vc<pi> up(xy.bg+m,xy.ed);
	
	int ans=kmzk(w,h,mx,my,lw,up);
	
	for(auto&p:up)p.b-=my;
	
	chmax(ans,relka(w,my,mx,lw));
	chmax(ans,relka(w,h-my,mx,up));
	
	chmax(global,ans);
	return ans;
}

int waf(int w,int h,vc<pi> xy){
	int cut=max(max(xy[0].a,w-xy[0].a)+h,max(xy[0].b,h-xy[0].b)+w);
	if(cut<=global)return 0;
	int n=xy.size();
	if(n==1){
		return cut;
	}
	
	int m=n/2;
	
	int mx=xy[m].a;
	
	vc<pi> l(xy.bg,xy.bg+m);
	vc<pi> r(xy.bg+m,xy.ed);
	
	sort(all(xy),[](pi a,pi b){return a.b<b.b;});
	int ans=relka(w,h,mx,xy);
	
	for(auto&p:r)
		p.a-=mx;
	chmax(ans,waf(mx,h,l));
	chmax(ans,waf(w-mx,h,r));
	
	chmax(global,ans);
	return ans;
}

signed main(){
	cin.tie(0);
	ios::sync_with_stdio(0);
	cout<<fixed<<setprecision(20);
	
	int w,h,n;cin>>w>>h>>n;
	global=max(h,w);
	
	vc<pi> xy;
	rep(i,n){
		int x,y;cin>>x>>y;
		xy.eb(x,y);
	}
	
	sort(all(xy));
	
	int ans=waf(w,h,xy);
	
	cout<<ans*2<<endl;
}


Measured memory_bytes: 24664