/* -*- coding: utf-8 -*-
 *
 * 1647.cc:  No.1647 Travel in Mitaru city 2 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_H = 100000;
const int MAX_W = 100000;
const int MAX_N = 100000;
const int MAX_M = MAX_H + MAX_W;

/* typedef */

typedef vector<int> vi;
typedef deque<int> dqi;
typedef pair<int,int> pii;
typedef map<pii,int> mpii;

/* global variables */

int xs[MAX_N], ys[MAX_N], uxs[MAX_N], uys[MAX_N];
mpii pmap;
vi nbrs[MAX_M];
int ps[MAX_M], ds[MAX_M], cis[MAX_M];

/* subroutines */

/* main */

int main() {
  int h, w, n;
  scanf("%d%d%d", &h, &w, &n);

  for (int i = 0; i < n; i++) {
    scanf("%d%d", xs + i, ys + i);
    uxs[i] = xs[i], uys[i] = ys[i];
    pmap[pii(xs[i], ys[i])] = i;
  }
  sort(uxs, uxs + n);
  sort(uys, uys + n);
  int xn = unique(uxs, uxs + n) - uxs;
  int yn = unique(uys, uys + n) - uys;

  for (int i = 0; i < n; i++) {
    int xi = lower_bound(uxs, uxs + xn, xs[i]) - uxs;
    int yi = lower_bound(uys, uys + yn, ys[i]) - uys;
    nbrs[xi].push_back(xn + yi);
    nbrs[xn + yi].push_back(xi);
  }

  int m = xn + yn;

  memset(ds, -1, sizeof(ds));
  for (int st = 0; st < m; st++)
    if (ds[st] < 0) {
      ps[st] = -1, ds[st] = 0;
      vi pts;
      pts.push_back(st);

      for (int u = st; u >= 0;) {
	vi &nbru = nbrs[u];
	int up = ps[u];

	if (cis[u] < nbru.size()) {
	  int v = nbru[cis[u]++];
	  if (v != up) {
	    if (ds[v] < 0) {
	      ps[v] = u, ds[v] = ds[u] + 1;
	      pts.push_back(v);
	      u = v;
	    }
	    else if (ds[v] < ds[u]) {
	      dqi q;
	      for (int i = ds[v]; i <= ds[u]; i++) q.push_back(pts[i]);
	      if (q.front() >= xn) {
		q.push_back(q.front());
		q.pop_front();
	      }

	      int k = q.size();
	      printf("%d\n", k);

	      for (int i = 0; i < k; i++) {
		int q0 = q[i], q1 = q[(i + 1) % k];
		int xi, yi;
		if (q0 < xn) xi = q0, yi = q1 - xn;
		else xi = q1, yi = q0 - xn;
		int pi = pmap[pii(uxs[xi], uys[yi])];
		printf("%d%c", pi + 1, (i + 1 < k) ? ' ' : '\n');
	      }
	      return 0;
	    }
	  }
	}
	else {
	  pts.pop_back();
	  u = up;
	}
      }
    }

  puts("-1");
  return 0;
}