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#include <iostream>
#include <vector>
#include <numeric>
#include <set>

using namespace std;
#define orid second.second
#define li first
#define ri second.first
typedef long long laf;
set<pair<int, pair<int, int>>> lines; // <left,<right, num>>
vector<pair<int, int>> originals;
vector<bool> taken;
int N; int M;

bool sol() {
    auto line = lines.begin();
    if ((*line).li > 0) {
        return false;
    }
    while (line != lines.end()) {
        auto beg = line;
        auto longest = beg;
        while (beg != lines.end() && (*beg).li == (*line).li) {
            if ((*beg).ri > (*longest).ri) { // Take interval starting in line.first with max line.second (long boi)
                longest = beg;
            }
            beg++;
        }
        beg = longest;
        taken[(*longest).orid] = true;
        if ((*longest).ri >= M) {
            return true;
        }
        auto end = beg;
        while (end != lines.end() && (*end).li < (*beg).ri + 1) {
            // Find longest interval starting up to first moment after beg (last one to find new interval :(
            if ((*end).ri > (*longest).ri) { // Take interval starting in line.first with max line.second (long boi)
                longest = end;
            }
            end++;
        }
        if (longest == beg) /* if we didn't find anything that went past beginning return 0 */ {
            return false;
        }
        line = longest;
    }
}

int main() {
    cin >> N;
    for (int i = 0; i < N; ++i) {
        cin >> M;
        originals.clear();
        taken.clear();
        while (true) {
            int L, R;
            cin >> L >> R;
            if (L == 0 && R == L) {
                break;
            }
            if (R < 0) {
                continue;
            }
            originals.emplace_back(L, R);
            if (L < 0) {
                L = 0;
            }
            lines.emplace(L, make_pair(R, originals.size() - 1));
        }
        taken.resize(originals.size());
        if (!sol()) {
            cout << 0;
            if (i < N - 1) {
                cout << endl;
            }
            continue;
        };
        int took = std::accumulate(taken.begin(), taken.end(), 0);
        cout << took << endl;
        for (int t = 0; t < taken.size(); t ++) {
            if (taken[t]) {
                cout << originals[t].li << " " << originals[t].second << endl;
            }
        }
        if (i < N - 1) {
            cout << endl;
        }
    }
}