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

ostream& operator<<(ostream& os, vector<int>& input)
{
    for (auto i : input)
    {
        os << i << " ";
    }
    os << endl;
    return os;
}

int main()
{
    cin.tie(nullptr);
    cout.tie(nullptr);
    ios_base::sync_with_stdio(false);
    int n, m;
    cin >> n >> m;
    vector<int>vec(n + 1);
    for (size_t i = 0; i < m; i++)
    {
        int a, b;
        cin >> a >> b;
        vec[a]++;
        vec[b]--;
    }
    vec[n] = 1;
    int a = 0, b = 1, c = 0, d = 0;
    for (size_t i = 1; i < n + 1; i++)
    {
        vec[i] += vec[i - 1];
        if (vec[i] == 0) a++;
        else
        {
            if (a > c)
            {
                c = a;
                d = b;
            }
            b = i + 1;
            a = 0;
        }
    }
    if (c == 0) cout << -1 << endl;
    else if (c == 1) cout << 1 << " " << d + 1 << endl;
    else cout << c - 1 << " " << d + 1 << endl;
    return 0;
}
/*
50 6
3 20
45 46
28 30
12 20
40 48
8 12

*/