// Source: https://usaco.guide/general/io

#include <bits/stdc++.h>
using namespace std;

int main() {
	int n, m;
	cin >> n >> m;
	vector<pair<int, int>> war(m);
	for (int i = 0; i < m; i++) {
		cin >> war[i].first >> war[i].second;
	}

	sort(war.begin(), war.end());
	int end = 0, maxh = 0, maxk = 0;
	for (int i = 0; i < m; i++) {
		if (war[i].first > end + 1) {
			if (war[i].first - end - 1 > maxh) {
				maxh = war[i].first - end - 1;
				maxk = end + 1;
			}
		}

		if (war[i].second > end) end = war[i].second;
	}

	if (maxh == 0) cout << -1;
	else cout << maxh << " " << maxk; 
}