4
1 2 4 3
 4
2 1 4 3
 10
1 2 10 9 7 4 8 3 6 5
 10
1 7 10 6 5 2 3 8 9 4
 4
4 3 2 1
 4
2 1 3 4
 10
1 10 9 5 3 2 4 7 8 6
 4
2 3 1 4
 4
2 4 3 1
 10
1 5 10 8 4 3 9 2 7 6
 4
1 4 3 2
 10
1 8 10 6 2 4 9 3 7 5
 4
2 3 4 1
 10
2 6 10 1 9 7 4 8 5 3
 4
4 1 2 3
 10
1 9 10 5 6 7 3 8 4 2
 4
4 2 1 3
 4
3 1 4 2
 10
1 2 3 4 6 5 7 9 10 8
 4
4 3 1 2
 4
1 3 4 2
 10
2 5 10 3 6 4 9 1 8 7
 10
2 1 10 5 8 4 9 3 7 6
 4
3 1 2 4
 10
1 6 10 7 9 5 3 8 4 2
 2
1 2
 10
1 3 10 9 4 7 5 8 6 2
 4
1 3 2 4
 4
4 2 3 1
 4
3 2 1 4
 4
3 2 4 1
 4
1 2 3 4
 10
2 7 10 1 6 3 4 8 9 5
 2
2 1
 4
3 4 2 1
 4
3 4 1 2
 10
10 1 9 2 8 3 7 4 6 5
 10
1 4 10 8 9 2 3 6 7 5
 10
2 3 10 5 4 8 6 9 7 1
 108
1 102 33 99 6 83 4 20 61 100 76 71 44 9 24 87 57 2 81 82 90 85 12 30 66 53 47 36 43 29 31 64 96 84 77 23 93 78 58 68 42 55 13 70 62 19 92 14 10 65 63 75 91 48 11 105 37 50 32 94 18 26 52 89 104 106 86 97 80 95 17 72 40 22 79 103 25 101 35 51 15 98 67 5 34 69 54 27 45 88 56 16 46 60 74 108 21 41 73 39 107 59 3 8 28 49 7 38
 4
4 1 3 2
 4
2 4 1 3
 10
2 4 10 3 9 1 5 7 8 6
 4
1 4 2 3

2 0
 4 0
 26 5
 26 6
 4 1
 2 0
 20 7
 4 0
 2 1
 26 6
 4 0
 24 6
 0 1
 28 1
 0 3
 26 1
 2 3
 4 1
 6 0
 2 2
 2 1
 28 0
 28 0
 2 3
 24 4
 0 0
 22 1
 2 0
 4 1
 4 0
 2 1
 0 0
 20 7
 0 1
 2 2
 0 2
 24 7
 20 5
 14 1
 3428 30
 2 3
 2 2
 28 0
 4 0

#include <bits/stdc++.h>
using namespace std;
static const int maxN = 1e5 + 10;
static const int dx[] = {-1, 0, 1, 0};
static const int dy[] = {0, 1, 0, -1};
template <class T>
bool inside(T a, T b, T c) {
  return a <= b && b <= c;
}
int n, m, k, source;
int x[maxN], y[maxN], d[maxN];
vector<pair<int, int> > a[maxN];
map<pair<int, int>, int> id;
void Enter() {
  scanf("%d%d%d", &n, &m, &k);
  for (int i = 0; i < k; ++i) {
    scanf("%d%d", &x[i], &y[i]);
    x[i]--;
    y[i]--;
    id[make_pair(x[i], y[i])] = i;
  }
}
void addEdge(int i, int j, int w) {
  a[i].push_back(make_pair(w, j));
  a[j].push_back(make_pair(w, i));
}
void Init() {
  for (int i = 0; i < k; ++i) {
    for (int j = -1; j <= 1; ++j) {
      if (inside(0, x[i] + j, n - 1)) addEdge(i, k + x[i] + j, 1);
      if (inside(0, y[i] + j, m - 1)) addEdge(i, k + n + y[i] + j, 1);
    }
    for (int j = 0; j < 4; ++j)
      if (id.count(make_pair(x[i] + dx[j], y[i] + dy[j]))) {
        addEdge(i, id[make_pair(x[i] + dx[j], y[i] + dy[j])], 0);
      }
  }
  if (id.count(make_pair(n - 1, m - 1))) {
    source = id[make_pair(n - 1, m - 1)];
  } else {
    source = k + n + m;
    addEdge(k + n + m, k + n - 1, 1);
    addEdge(k + n + m, k + n + m - 1, 1);
  }
  for (int i = 0; i < k + n + m + 1; ++i) d[i] = 2e9;
}
void Process() {
  priority_queue<pair<int, int> > q;
  q.push(make_pair(0, 0));
  d[0] = 0;
  while (!q.empty()) {
    int u = q.top().second, du = -q.top().first;
    q.pop();
    if (d[u] != du) continue;
    if (u == source) {
      break;
    }
    for (auto it : a[u]) {
      int v = it.second, dv = it.first;
      if (d[v] > d[u] + dv) {
        d[v] = d[u] + dv;
        q.push(make_pair(-d[v], v));
      }
    }
  }
  if (d[source] == 2e9)
    puts("-1");
  else
    printf("%d\n", (d[source] + 1) / 2);
}
int main() {
  Enter();
  Init();
  Process();
  return 0;
}
