#include <iostream>
#include <vector>
using namespace std;

int main()
{
	int linesNum = 0;
	int stationsNum = 0;
	cin >> linesNum;
	cin >> stationsNum;
	vector<pair<int, int>> stations(stationsNum, { 0,0 });
	for (int i = 0; i < linesNum; i++) {
		int start = 0;
		int end = 0;
		cin >> start >> end;
		for (int j = start - 1; j < end -1; j++) {
			if (stations[j].second < end) {
				stations[j] = pair<int, int>(i, end - 1);

			}
			else break;
		}

	}
	vector<int> takenLines(0, 0);
	for (int i = 0; i + 1 < stationsNum; i) {
		if (stations[i] == pair<int, int>(0, 0)) {
			
				cout << -1;
				return 0;
			
		}else {
			takenLines.push_back(stations[i].first);
			i = stations[i].second;
		}
	}
	cout << takenLines.size() - 1 << endl;
		for (int i : takenLines) {
			cout << i + 1 << ' ';
		}
	return 0;
}