#include <bits/stdc++.h>
#include<atcoder/all>
using namespace atcoder;
using namespace std;
using ll = long long;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;
using vvvvll = vector<vvvll>;
using vb = vector<bool>;
using vvb = vector<vb>;
using vvvb = vector<vvb>;
using vvvvb = vector<vvvb>;
using vvvvvb = vector<vvvvb>;
#define all(A) A.begin(),A.end()
#define rep(i, n) for (ll i = 0; i < (ll) (n); i++)
template<class T>
bool chmax(T& p, T q, bool C = 1) {
    if (C == 0 && p == q) {
        return 1;
    }
    if (p < q) {
        p = q;
        return 1;
    }
    else {
        return 0;
    }
}
template<class T>
bool chmin(T& p, T q, bool C = 1) {
    if (C == 0 && p == q) {
        return 1;
    }
    if (p > q) {
        p = q;
        return 1;
    }
    else {
        return 0;
    }
}
ll modPow(long long a, long long n, long long p) {
    if (n == 0) return 1; // 0乗にも対応する場合
    if (n == 1) return a % p;
    if (n % 2 == 1) return (a * modPow(a, n - 1, p)) % p;
    long long t = modPow(a, n / 2, p);
    return (t * t) % p;
}
ll gcd(ll(a), ll(b)) {
    if (a == 0)return b;
    if (b == 0)return a;
    ll c = a;
    while (a % b != 0) {
        c = a % b;
        a = b;
        b = c;
    }
    return b;
}
ll sqrtz(ll N) {
    ll L = 0;
    ll R = sqrt(N) + 10000;
    while (abs(R - L) > 1) {
        ll mid = (R + L) / 2;
        if (mid * mid <= N)L = mid;
        else R = mid;
    }
    return L;
}

bool DEB = 0;

using mint = modint1000000007;
using vm = vector<mint>;
using vvm = vector<vm>;
using vvvm = vector<vvm>;


vector<mint> fact, factinv, inv, factK;
const ll mod = 1e9 + 7;
void prenCkModp(ll n) {
    //factK.resize(4*n+5);
    fact.resize(n + 5);
    factinv.resize(n + 5);
    inv.resize(n + 5);
    fact[0] = fact[1] = 1;
    factinv[0] = factinv[1] = 1;
    inv[1] = 1;
    for (ll i = 2; i < n + 5; i++) {
        fact[i] = (fact[i - 1] * i);
        inv[i] = (mod - ((inv[mod % i] * (mod / i))));
        factinv[i] = (factinv[i - 1] * inv[i]);
    }
    //factK[0]=1;
    //for(ll i=1;i<4*n+5;i++){
    //    factK[i]=factK[i-1]*mint(K-i+1);
    //    //K*(K-1)*...*(K-i+1);
    //}
}
mint nCk(ll n, ll k) {
    if (n < k || k < 0) return 0;
    return (fact[n] * ((factinv[k] * factinv[n - k])));
}
//mint nCkK(ll n,ll k){
//    if(K<n||K-n<k)return 0;
//    mint res=factK[n+k];
//    res*=factK[n].inv();
//    res*=factinv[k];
//    return res;
//}



int main() {

    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    ll H,W,N;
    cin>>H>>W>>N;
    vll A(N),B(N),C(N),D(N);
    rep(i,N)cin>>A[i]>>B[i]>>C[i]>>D[i];
    map<pair<ll,ll>,ll> M;
    M[{1,1}]=1;
    M[{H,W}]=1;
    rep(i,N)M[{A[i],B[i]}]=M[{C[i],D[i]}]=1;
    ll cnt=0;
    for(auto m:M)M[m.first]=cnt,cnt++;
    vector<vector<pair<ll,ll>>> G(cnt);
    rep(i,N){
        ll U=M[{1,1}];
        ll V=M[{A[i],B[i]}];
        G[U].push_back({V,abs(A[i]-1)+abs(B[i]-1)});
        U=M[{C[i],D[i]}];
        G[V].push_back({U,1});
        V=M[{H,W}];
        G[U].push_back({V,abs(H-C[i])+abs(W-D[i])});
        rep(j,N){
            U=M[{C[i],D[i]}];
            V=M[{A[j],B[j]}];
            G[U].push_back({V,abs(A[j]-C[i])+abs(B[j]-D[i])});
        }
    }
    G[0].push_back({cnt-1,H+W-2});
    vll DP(cnt,1e18);
    DP[0]=0;
    priority_queue<pair<ll,ll>,vector<pair<ll,ll>>,greater<pair<ll,ll>>> Q;
    Q.push({0,0});
    vb seen(cnt,0);
    while(!Q.empty()){
        ll c=Q.top().first;
        ll n=Q.top().second;
        Q.pop();
        if(seen[n])continue;
        seen[n]=1;
        for(auto vw:G[n]){
            ll v=vw.first;
            ll w=vw.second;
            if(seen[v])continue;
            if(chmin(DP[v],c+w)){
                Q.push({c+w,v});
            }
        }
    }
    cout<<DP[cnt-1]<<endl;
}