#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
template<class T> using V = vector<T>;
using VI = V<int>;
using VL = V<ll>;
using VS = V<string>;
template<class T> using PQ = priority_queue<T, V<T>, greater<T>>;
using graph = V<VI>;
template<class T> using w_graph = V<V<pair<int, T>>>;
#define FOR(i,a,n) for(int i=(a);i<(n);++i)
#define eFOR(i,a,n) for(int i=(a);i<=(n);++i)
#define rFOR(i,a,n) for(int i=(n)-1;i>=(a);--i)
#define erFOR(i,a,n) for(int i=(n);i>=(a);--i)
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define out(y,x) ((y)<0||h<=(y)||(x)<0||w<=(x))
#ifdef _DEBUG
#define line cout << "-----------------------------\n"
#define stop system("pause")
#endif
constexpr ll INF = 1000000000;
constexpr ll LLINF = 1LL << 61;
constexpr ll mod = 1000000007;
constexpr ll MOD = 998244353;
constexpr ld eps = 1e-10;
template<class T>inline bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; }return false; }
template<class T>inline bool chmin(T& a, const T& b) { if (a > b) { a = b; return true; }return false; }
inline void init() { cin.tie(nullptr); cout.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); }
template<class T>inline istream& operator>>(istream& is, V<T>& v) { for (auto& a : v)is >> a; return is; }
template<class T, class U>inline istream& operator>>(istream& is, pair<T, U>& p) { is >> p.first >> p.second; return is; }
template<class T>inline V<T> vec(size_t a) { return V<T>(a); }
template<class T>inline V<T> defvec(T def, size_t a) { return V<T>(a, def); }
template<class T, class... Ts>inline auto vec(size_t a, Ts... ts) { return V<decltype(vec<T>(ts...))>(a, vec<T>(ts...)); }
template<class T, class... Ts>inline auto defvec(T def, size_t a, Ts... ts) { return V<decltype(defvec<T>(def, ts...))>(a, defvec<T>(def, ts...)); }
template<class T>inline void print(const T& a) { cout << a << "\n"; }
template<class T, class... Ts>inline void print(const T& a, const Ts&... ts) { cout << a << " "; print(ts...); }
template<class T>inline void print(const V<T>& v) { for (int i = 0; i < v.size(); ++i)cout << v[i] << (i == v.size() - 1 ? "\n" : " "); }
template<class T>inline void print(const V<V<T>>& v) { for (auto& a : v)print(a); }
template<class T>inline T sum(const V<T>& a, int l, int r) { return 0 <= l && l <= r && r < a.size() ? a[r] - (l == 0 ? 0 : a[l - 1]) : 0; }
template<class T>inline void END(T s) { print(s); exit(0); }
void END() { exit(0); }

template<int M> class Indexer {
    static_assert(M > 0, "M must be positive");
    array<int, M> lim;
    int siz;
public:
    Indexer(initializer_list<int> lim_init) {
        assert(lim_init.size() == M);
        copy(all(lim_init), lim.begin());
        siz = 1;
        FOR(i, 0, M) {
            assert(lim[i] > 0);
            siz *= lim[i];
        }
    };
    int operator() (initializer_list<int> target_init) {
        assert(target_init.size() == M);
        array<int, M> target;
        copy(all(target_init), target.begin());
        int res = 0;
        FOR(i, 0, M)res = res * lim[i] + target[i];
        return res;
    }
    array<int, M> operator() (int a) {
        assert(a < size());
        array<int, M> res;
        rFOR(i, 0, M) {
            res[i] = a % lim[i];
            a /= lim[i];
        }
        return res;
    }
    int size() {
        return siz;
    }
};

int main() {
    init();

    int h, w, n; cin >> h >> w >> n;
    VI x(n), y(n);
    V<V<pair<int, int>>> gyo(h), ret(w);
    FOR(i, 0, n) {
        cin >> x[i] >> y[i];
        --x[i], --y[i];
        gyo[y[i]].emplace_back(x[i], i);
        ret[x[i]].emplace_back(y[i], i);
    }

    Indexer<2> indexer({ 2,n });
    graph g(indexer.size());
    FOR(i, 0, n) {
        g[indexer({ 0,i })].push_back(indexer({ 1,i }));
        g[indexer({ 1,i })].push_back(indexer({ 0,i }));
    }
    FOR(i, 0, h) {
        sort(all(gyo[i]));
        FOR(j, 1, gyo[i].size()) {
            g[indexer({ 0,gyo[i][j - 1].second })].push_back(indexer({ 0,gyo[i][j].second }));
            g[indexer({ 0,gyo[i][j].second })].push_back(indexer({ 0,gyo[i][j - 1].second }));
        }
    }
    FOR(i, 0, w) {
        sort(all(ret[i]));
        FOR(j, 1, ret[i].size()) {
            g[indexer({ 1,ret[i][j - 1].second })].push_back(indexer({ 1,ret[i][j].second }));
            g[indexer({ 1,ret[i][j].second })].push_back(indexer({ 1,ret[i][j - 1].second }));
        }
    }

    VI seen(g.size());
    deque<int> ans;
    int root = -1;
    auto dfs = [&](auto&& f, int cur, int par)->bool {
        seen[cur] = 1;
        for (int to : g[cur]) {
            if (to == par || seen[to] == 2)continue;
            if (seen[to] == 0) {
                if (f(f, to, cur)) {
                    if (indexer(cur)[1] == indexer(to)[1]) {
                        ans.push_back(indexer(cur)[1]);
                    }
                    if (root == cur) {
                        if (y[ans[0]] != y[ans[1]]) {
                            ans.push_back(ans.front());
                            ans.pop_front();
                        }
                        print(ans.size());
                        FOR(i, 0, ans.size()) {
                            if (i)cout << " ";
                            cout << ans[i] + 1;
                        }
                        cout << "\n";
                        exit(0);
                    }
                    else {
                        return true;
                    }
                }
            }
            else if (seen[to] == 1) {
                root = to;
                if (indexer(cur)[1] == indexer(to)[1]) {
                    ans.push_back(indexer(cur)[1]);
                }
                return true;
            }
        }
        seen[cur] = 2;
        return false;
    };
    FOR(i, 0, g.size())if (seen[i] == 0)dfs(dfs, i, -1);
    print(-1);

    return 0;
}