#include <algorithm>
#include <iostream>
#include <vector>

using namespace std;

int main() {
    int m, left, right, maxRight = 0, pos = 0;
    cin >> m;

    vector <pair <int, int> > segs, answer;
    while (cin >> left >> right) {
        segs.push_back(make_pair(left, right));
    }

    sort(segs.begin(), segs.end());

    while (maxRight < m) {
        int currLeft, currRight = maxRight;

        while (pos != segs.size() && segs[pos].first <= maxRight) {
            if (currRight < segs[pos].second) {
                currLeft = segs[pos].first;
                currRight = segs[pos].second;
            }
            ++pos;
        }

        if (currRight == maxRight) {
            cout << "No solution\n";
            return 0;
        }

        answer.push_back(make_pair(currLeft, currRight));
        maxRight = currRight;
    }

    cout << answer.size() << '\n';
    for (auto const &i : answer) {
        cout << i.first << ' ' << i.second << '\n';
    }

    return 0;
}