#include<bits/stdc++.h>
#define fi first
#define se second
#define pb push_back
#define pf push_front
#define popb pop_back
#define popf pop_front
#define ins insert
#define pq priority_queue
#define minele min_element
#define maxele max_element
#define lb lower_bound //first pos >= val
#define ub upper_bound // first pos > val
#define cnt_bit __builtin_popcount
#define debug(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "
//#pragma GCC optimize("Ofast")
//#pragma GCC target("avx,avx2,fma")
using namespace std;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

typedef long long ll;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;


int d4x[4] = {1, 0, -1, 0}; int d4y[4] = {0, 1, 0, -1};
int d8x[8] = {0, 1, 1, 1, 0, -1, -1, -1};
int d8y[8] = {1, 1, 0, -1, -1, -1, 0, 1};

const ll oo = 1e18;
const ll maxN = 1e6;

/* Author : Le Ngoc Bao Anh, 10A5, LQD High School for Gifted Student */

void maximize(int &a, int b) {
    a = max(a, b);
}

void minimize(int &a, int b) {
    a = min(a, b);
}

const int N = 2e5 + 10;
struct P {
    int x, y, id;
} a[N];
ll dp[N][2];
vector<pii> g[N][2];

void solve() {
    int n, m, k;
    cin >> n >> m >> k;

    bool ok1 = false, ok2 = false;
    for(int i = 1; i <= k; i++) {
        cin >> a[i].x >> a[i].y; a[i].id = i;
        if(a[i].x == 1 && a[i].y == 1) ok1 = true;
        if(a[i].x == n && a[i].y == m) ok2 = true;
    }

    a[++k] = {1, 1, k};
    a[++k] = {n, m, k};
    sort(a + 1, a + 1 + k, [&](P _a, P _b) {if(_a.x == _b.x) return _a.y < _b.y; return _a.x < _b.x;});
    for(int i = 2; i <= k; i++) {
        if(a[i].x == a[i - 1].x) {
            g[a[i].id][0].pb(make_pair(a[i - 1].id, abs(a[i].y - a[i - 1].y)));
            g[a[i - 1].id][0].pb(make_pair(a[i].id, abs(a[i].y - a[i - 1].y)));
        }
    }

    sort(a + 1, a + 1 + k, [&](P _a, P _b) {if(_a.y == _b.y) return _a.x < _b.x; return _a.y < _b.y;});
    for(int i = 2; i <= k; i++) {
        if(a[i].y == a[i - 1].y) {
            g[a[i].id][1].pb(make_pair(a[i - 1].id, abs(a[i].x - a[i - 1].x)));
            g[a[i - 1].id][1].pb(make_pair(a[i].id, abs(a[i].x - a[i - 1].x)));
        }
    }

    for(int i = 1; i <= k; i++) {
        dp[i][0] = dp[i][1] = oo;
    }

    dp[k - 1][0] = 0;
    struct PQ {
        int u, turn;
        ll w;

        bool operator < (const PQ & temp) const {
            return w >   temp.w;
        }
    };
    pq<PQ> q;
    q.push({k - 1, 0, 0});

    while(!q.empty()) {
        PQ curr = q.top(); q.pop();
        int u = curr.u, turn = curr.turn; ll f = curr.w;
        if(u == k - 1) {
            if(ok1 && dp[u][turn ^ 1] > dp[u][turn] + 1) {
                dp[u][turn ^ 1] = dp[u][turn] + 1;
                q.push({u, turn ^ 1, dp[u][turn ^ 1]});
            }
        } else
        if(u == k) {
            if(ok2 && dp[u][turn ^ 1] > dp[u][turn] + 1) {
                dp[u][turn ^ 1] = dp[u][turn] + 1;
                q.push({u, turn ^ 1, dp[u][turn ^ 1]});
            }
        } else
        if(dp[u][turn ^ 1] > dp[u][turn] + 1) {
            dp[u][turn ^ 1] = dp[u][turn] + 1;
            q.push({u, turn ^ 1, dp[u][turn ^ 1]});
        }

        for(int i = 0; i < g[u][turn].size(); i++) {
            int v = g[u][turn][i].fi, w = g[u][turn][i].se;
            if(dp[v][turn] > dp[u][turn] + w) {
                dp[v][turn] = dp[u][turn] + w;
                q.push({v, turn, dp[v][turn]});
            }
        }
    }

    cout << (min(dp[k][0], dp[k][1]) < oo ? min(dp[k][0], dp[k][1]) : -1);
}

int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    #ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
    #else
    //online
    #endif

    int tc = 1, ddd = 0;
    // cin >> tc;
    while(tc--) {
        //ddd++;
        //cout << "Case #" << ddd << ": ";
        solve();
    }
}