#include <iostream>
#include <vector>

using namespace std;

long long n, m, i, j, a, b, maxi;

int main()
{
    cin >> m >> n;
    vector <long long> x(n + 1);
    vector <long long> honnan(n + 1);
    vector <long long> v;

    for (i = 1; i <= m; ++i)
    {
        cin >> a >> b;
        if (x[a] <= b)
        {
            x[a] = b;
            honnan[a] = i;
        }
    }

    i = 1;
    while (x[i]<n)
    {
        v.push_back(honnan[i]);
        maxi = i;
        
        for (j = i+1; j <= x[i]; ++j)
        {
            if (x[j] > x[maxi])
            {
                maxi = j;
            }
        }
        
        if (x[maxi] <= x[i])
        {
            cout << "-1";
            return 0;
        }

        i = maxi;
    }

    v.push_back(honnan[maxi]);

    cout << v.size() - 1 << "\n";
    for (auto& e : v) cout << e << " ";

    return 0;
}