#include <bits/stdc++.h>
#include <ios>
#include <iostream>
using namespace std;
using ll = long long;
using P = pair<ll, ll>;
#define f first
#define s second
const ll MOD = 998244353;
ll d(ll x1, ll y1, ll x2, ll y2) {
return abs(x1-x2) + abs(y1-y2);
}
int main() {
ll X, Y; cin >> X >> Y;
int n; cin >> n;
vector<pair<P, P>> pts;
vector<P> dp(n+1, {1e9, 1e9});
dp[0] = {0, 0};
for (int i = 0; i < n; i++) {
ll a, b, c, d;
cin >> a >> b >> c >> d;
ll x_lo = min(a, c), x_hi = max(a, c);
ll y_lo = min(b, d), y_hi = max(b, d);
pts.push_back({{x_lo - 1, x_hi + 1}, {y_lo - 1, y_hi + 1}});
}
sort(pts.begin(), pts.end());
// for (auto x: pts) {
// cout << x.f.f << ", " << x.f.s << ", " << x.s.f << ", " << x.s.s << "\n";
// }
// cout << "\n";
set<pair<ll, ll>> y;
y.insert({0, 0}); // <y=k, ith rect>
for (int i = 0; i < n; i++) {
// cout << "Y: " << "\n";
// for (auto it: y) {
// cout << it.f << ", " << it.s << "\n";
// }
ll x = pts[i].f.f;
if (x > X) break;
ll b = pts[i].s.f;
ll t = pts[i].s.s;
auto it1 = y.lower_bound({b, 0});
auto it2 = y.upper_bound({t, 1e9});
vector<pair<ll, ll>> to_erase;
vector<pair<ll, ll>> to_insert;
for (auto it3 = it1; it3 != it2; it3++) {
pair<ll, ll> tp = (*it3);
if (tp.s == 0) {
dp[i+1].f = min(dp[i+1].f, dp[tp.s].f+d(0, 0, x, b));
dp[i+1].s = min(dp[i+1].s, dp[tp.s].f+d(0, 0, x, t));
// cout << "b, i+1: " << b << ", " << i+1 << "\n";
// cout << "t, i+1: " << t << ", " << i+1 << "\n";
to_insert.push_back({b, i+1});
to_insert.push_back({t, i+1});
to_erase.push_back(tp);
} else {
ll rect = tp.s-1;
ll st = pts[rect].f.f;
ll vl = (tp.f == pts[rect].s.f) ? dp[tp.s].f : dp[tp.s].s;
dp[i+1].f = min(dp[i+1].f, vl+d(st, tp.f, x, b));
dp[i+1].s = min(dp[i+1].s, vl+d(st, tp.f, x, t));
// cout << "b2, i+1: " << b << ", " << i+1 << "\n";
// cout << "t2, i+1: " << t << ", " << i+1 << "\n";
to_insert.push_back({b, i+1});
to_insert.push_back({t, i+1});
to_erase.push_back(tp);
}
}
for (auto it: to_insert) {
y.insert(it);
}
for (auto it: to_erase) {
y.erase(it);
}
}
ll mn = 1e9;
for (auto it: y) {
// cout << it.f << ", " << it.s << ", " << dp[it.s].f << ", " << dp[it.s].s << "\n";
ll vl = (it.f == pts[it.s-1].s.f) ? dp[it.s].f : dp[it.s].s;
// cout << "it.f, vl: " << it.f << ", " << vl << "\n";
// cout << "pts[it.s-1].f.f, it.f: " << pts[it.s-1].f.f << ", " << it.f << "\n";
mn = min(mn, vl+d(pts[it.s-1].f.f, it.f, X, Y));
}
cout << mn;
}
