#include <vector>
#include "optimization.h"

using namespace std;

int main() {
    int m = readInt();
    vector<pair<int, int>> arr, ans;
    while(true) {
        int a = readInt(), b =readInt();
        if(a == 0 && b == 0) {
            break;
        }
        arr.emplace_back(a, b);
    }
    sort(arr.begin(), arr.end());
    int curR = 0;
    for (int i = 0; i < arr.size(); ++i) {
        int lbound = arr[i].first;
        if(lbound > curR) {
            if(i == 0 || arr[i-1].second <=curR) {
                writeWord("No solution\n");
                return 0;
            } else {
                curR = arr[i-1].second;
                ans.push_back(arr[i-1]);
                if(curR >= m) {
                    break;
                }
            }
        }
    }
    if(curR < m) {
        if(arr[arr.size() - 1].second < m) {
            //writeWord("No solution\n");
            return 1;
        }
        ans.push_back(arr[arr.size() - 1]);
    }

    writeInt(ans.size(), '\n');
    for(auto p : ans) {
        writeInt(p.first, ' ');
        writeInt(p.second, '\n');
    }
    return 0;
}