#include <fstream>
#include <unordered_map>
#include <iterator>
using namespace std;
ifstream fin("pariuri.in");
ofstream fout("pariuri.out"); 

//problema de hashing
//folosim unordered map cu elemente de forma (moment de timp, suma totala castigata)

unordered_map <int, int> perechi;
int N, M, timp, bani;

void Citire()
{
    fin >> N;
    for (int i = 0; i < N; ++i)
    {
        fin >> M;
        //adaugam la suma specifica momentului de timp suma de bani tocmai citita
        for (int j = 0; j < M; ++j)      { fin >> timp >> bani;  perechi[timp] += bani; }  
    }
}

void Afisare()
{
    fout << perechi.size() << "\n";
    for (auto i = perechi.begin(); i != perechi.end(); ++i) fout << i->first << " " << i->second << " ";
}

int main()
{
    Citire();
    Afisare();
    return 0;
}