#include <iostream>
#include <queue>
#include <algorithm>
#define ll long long

using namespace std;

int main()
{
    ll n, m;
    cin >> n >> m;
    vector <ll> a(n + 1), b(n + 1);
    for (ll i = 1; i <= n; ++i)
    {
        cin >> a[i] >> b[i];
    }
    ll j = 1;
    deque <ll> res(1), poz;
    res[0] = 0;
    ll maxi = 1, db;
    b[0] = 999999;
    for (ll i = 1; i <= m; ++i)
    {
        db = 0;
        if (maxi > b[j])
        {
            ++j;
            continue;
        }
        while (a[j] == i && maxi <= b[j] && maxi >= a[j])
        {
            if (maxi == b[j])
            {
                break;
            }
            ++db;
            poz.push_front(j);
            res.push_front(b[j]);
            if (res.front() <= b[j])
            {
                if (maxi < b[j])
                    maxi = b[j];
            }
            if (maxi > b[j - 1] && db > 1)
            {
                poz.erase(poz.begin() + j - 1);
                res.erase(res.begin() + j - 1);
            }
            ++j;
        }

    }

    if (res.front() == m)
    {
        cout << poz.size() - 1 << endl;
        for (ll i = poz.size() - 1; i >= 0; --i)
        {
            cout << poz[i] << " ";
        }
    }
    else
        cout << "-1";

    return 0;
}
/*
6 9
1 2
1 4
2 6
3 4
4 5
7 9
*/