#include <bits/stdc++.h>
#define ll long long
#define fi first
#define se second
using namespace std;
bool cmp(pair<ll,ll> x, pair<ll,ll>y){
if(x.fi==y.fi) return x.se<y.se;
return x.fi<y.fi;
}
pair<ll,ll> a[5005];
map<ll,ll> mp1,mp2;
vector<pair<ll,ll>> ans[10];
int main() {
ll n,r,c,res=INT_MAX;
cin>>r>>c;
cin>>n;
for(ll i=1;i<=n;i++){
cin>>a[i].fi>>a[i].se;
}
for(ll i=1;i<=n;i++){
vector<ll> b;
ll d,l;
l=d=0;
// c.push_back(0);
// c=b;
if(mp1[a[i].fi]==0){
ll h1=0,h2=0;
for(ll j=1;j<=n;j++){
if(a[i].fi == a[j].fi){
b.push_back(a[j].se);
}
}
// for(ll x:b) cout<<x<<' ';
// b.push_back(c+1);
sort(b.begin(),b.end());
for(ll j=0;j<b.size()-1;j++){
if(b[j+1] - b[j] -1 <= d) continue;
d = b[j+1] - b[j] -1;
// cout<<1;
}
h1 = b.back() - b[0] +1;
if(c - b.back() >= d){
h1 += d;
}
else{
h1 += c - b[b.size()-1];
}
if(c-(b[0]+h1-1) > b[0]-1 ) ans[1].push_back({c-h1 + d,a[i].fi});
else ans[2].push_back({c-h1 + d,a[i].fi});
// cout<<c<<' '<<h1<<' '<<d<<' '<<c-h1 + d<<endl;
for(ll j=b.size()-1;j>0;j--){
if(b[j] - b[j-1] -1 <= l) continue;
l = b[j] - b[j-1] -1;
}
h2 = b[b.size()-1] - b[0] +1;
if(b[0] -1 >= l){
h2 += l;
}
else{
h2 += b[0] -1;
}
if(c-(b[0]+h2-1) > b[0]-1 ) ans[1].push_back({c-h2 + l,a[i].fi});
else ans[2].push_back({c-h2 + l,a[i].fi});
// cout<<c-h2 + l<<endl;
mp1[a[i].fi]++;
}
d=l=0;
b.clear();
if(mp2[a[i].se]==0){
ll h1=0,h2=0;
for(ll j=1;j<=n;j++){
if(a[i].se == a[j].se){
b.push_back(a[j].fi);
}
}
// b.push_back(c+1);
sort(b.begin(),b.end());
for(ll j=0;j<b.size()-1;j++){
if(b[j+1] - b[j] -1 <= d) continue;
d = b[j+1] - b[j] -1;
}
h1 = b[b.size()-1] - b[0] +1;
if(r - b[b.size()-1] >= d){
h1 += d;
}
else{
h1 += r - b[b.size()-1];
}
if(r-(b[0]+h1-1) > b[0]-1 ) ans[3].push_back({r-h1 + d,a[i].fi});
else ans[4].push_back({r-h1 + d,a[i].fi});
// cout<<c-h1 + d<<endl;
for(ll j=b.size()-1;j>0;j--){
if(b[j] - b[j-1] -1 <= l) continue;
l = b[j] - b[j-1] -1;
}
h2 = b[b.size()-1] - b[0] +1;
if(b[0] -1 >= l){
h2 += l;
}
else{
h2 += b[0] -1;
}
if(r-(b[0]+h2-1) > b[0]-1 ) ans[1].push_back({r-h1 + d,a[i].fi});
else ans[2].push_back({r-h1 + d,a[i].fi});
// c.push_back(r+1);
// cout<<c-h2 + l<<endl;
mp2[a[i].se]++;
}
b.clear();
}
for(ll i=1;i<=4;i++){
sort(ans[i].begin(),ans[i].end(),cmp);
ll m=0,ans1=INT_MAX,d,l;
d=l=0;
vector<ll>b;
while(m<ans[i].size() && ans[i][m].fi==ans[i][0].fi){
b.push_back(ans[i][m].se);
m++;
}
// cout<<m;
// for(pair<ll,ll> x : ans[i]){
// cout<<x.se<<' ';
// }
// cout<<endl;
if(m==0) continue;
if(i <= 2){
ll h1=0,h2=0;
for(ll j=0;j<b.size()-1;j++){
if(b[j+1] - b[j] -1 <= d) continue;
d = b[j+1] - b[j] -1;
}
// cout<<d<<' ';
h1 = b.back() - b[0] +1;
if(r - b.back() >= d){
h1 += d;
}
else{
h1 += r - b[b.size()-1];
}
ans1 = min(ans1,r-h1 + d);
for(ll j=b.size()-1;j>0;j--){
if(b[j] - b[j-1] -1 <= l) continue;
l = b[j] - b[j-1] -1;
}
h2 = b[b.size()-1] - b[0] +1;
if(b[0] -1 >= l){
h2 += l;
}
else{
h2 += b[0] -1;
}
ans1 = min(ans1,r-h2 + l);
}
else{
ll h1=0,h2=0;
for(ll j=0;j<b.size()-1;j++){
if(b[j+1] - b[j] -1 <= d) continue;
d = b[j+1] - b[j] -1;
}
h1 = b.back() - b[0] +1;
if(c - b.back() >= d){
h1 += d;
}
else{
h1 += c - b[b.size()-1];
}
ans1 = min(ans1,c-h1 + d);
for(ll j=b.size()-1;j>0;j--){
if(b[j] - b[j-1] -1 <= l) continue;
l = b[j] - b[j-1] -1;
}
h2 = b[b.size()-1] - b[0] +1;
if(b[0] -1 >= l){
h2 += l;
}
else{
h2 += b[0] -1;
}
ans1 = min(ans1,c-h2 + l);
}
// cout<<ans1<<' '<<ans[i][0].fi<<'\n';
if(res>ans1 + ans[i][0].fi) res = ans1 + ans[i][0].fi ;
}
cout<<res;
return 0;
}
