#include <bits/stdc++.h>

using namespace std;

typedef pair<int, int> pii;

int main()
{
    int n, m;
    cin >> m >> n;

    vector<pii> eleri(n);
    int maxi = 0;
    for(int i = 0; i < m; i++){
        int a, b;
        cin >> a >> b;
        a--; b--;
        maxi = max(maxi, b);

        for(int j = a; j <= b; j++){
            if(eleri[j].first < b){
                eleri[j].first = b;
                eleri[j].second = i;
            }
        }
    }

    int akt = 0;
    vector<int> vonalak;
    while(akt < n - 1){
        if(akt == eleri[akt].first){
            cout << "-1\n";
            return 0;
        }

        vonalak.push_back(eleri[akt].second);
        akt = eleri[akt].first;
    }

    cout << vonalak.size() - 1 << "\n";
    for(int x : vonalak){
        cout << x + 1 << " ";
    }
    cout << "\n";
}