#include <bits/stdc++.h>
#include <atcoder/math>
using namespace std;
using namespace atcoder;
#define int long long
using vec_int = vector<int>;
using vec_ii = vector<vec_int>;
using vec_iii = vector<vec_ii>;
using vec_iiii = vector<vec_iii>;
using P = pair<int,int>;
using T = tuple<int,int,int>;
using ll = long long;
using ld = long double;
#define rep(i, n) for(int i = 0; i < (int)(n); i++)

void cout_line(vector<int> &a){
    for(int i=0;i<a.size();i++){
        if(i<a.size()-1){
            cout<<a.at(i)<<" ";
        }else{
            cout<<a.at(i)<<endl;
        }
    }
}

int charToInt(char c){
    char zero_num = '0';
    return (int)c - (int)zero_num;
}

signed main(){
    int H, W, N;
    cin>>H>>W>>N;
    vec_int x(N), y(N); 
    rep(i,N)cin>>x.at(i)>>y.at(i);

    vector<vec_int> x_city(H+1);
    vector<vec_int> y_city(W+1);

    rep(i, N){
        x_city.at(x.at(i)).push_back(i);
        y_city.at(y.at(i)).push_back(i);
    }

    vec_int visited(N+1, -2);

    queue<T> que;
    for(int i=0;i<N;i++){
        if(visited.at(i)==-2){
            que.emplace(i, 0, -1);
            que.emplace(i, 1, -1);
        }else{
            continue;
        }

        int flag = 0;
        int pos1, pos2;
        map<int,int> visited_map;

        while(!que.empty()){
            int pos, direc, prev; tie(pos, direc, prev) = que.front(); que.pop();
            //cout<<"pos:"<<pos<<" "<<direc<<endl;
            if(visited_map.count(pos)){
                if(visited_map[pos]>=-1&&prev>=0){
                    pos1 = pos;
                    pos2 = prev;
                    flag = 1;
                    break;
                }
            }
            visited_map[pos] = prev;
            if(direc==0){
                for(auto next: x_city.at(x.at(pos))){
                    if(next==pos)continue;
                    if(visited.at(next)>0)continue;
                    que.emplace(next, 1, pos);
                }
            }else{
                for(auto next: y_city.at(y.at(pos))){
                    if(next==pos)continue;
                    if(visited.at(next)>0)continue;
                    que.emplace(next, 0, pos);
                }
            }
        }
        if(flag==0){
            for(auto temp:visited_map){
                visited.at(temp.first) = 1;
            }
            continue;
        }
        vec_int route1, route2;
        while(pos1>=0){
            route1.push_back(pos1);
            pos1 = visited_map[pos1];
        }
        reverse(route1.begin(), route1.end());

        while(pos2>=0){
            route2.push_back(pos2);
            pos2 = visited_map[pos2];
        }
        reverse(route2.begin(), route2.end());
        int ind = 0;
        for(int i=0;i<route1.size()&&i<route2.size();i++){
            ind = i;
            if(route1.at(i)!=route2.at(i))break;
        }
        vec_int ans; 
        for(int i=ind;i<route1.size();i++){
            ans.push_back(route1.at(i)+1);
        }
        reverse(ans.begin(), ans.end());
        ans.push_back(route1.at(ind-1)+1);
        for(int i=ind;i<route2.size();i++){
            ans.push_back(route2.at(i)+1);
        }
        cout<<ans.size()<<endl;
        cout_line(ans);


        return 0;
    }
    cout<<-1<<endl;



    return 0;
}