#include<iostream>
#include<fstream>
#include<vector>
#include<map>

using namespace std;

int timp[1000000];
int bani[1000000];
vector<long> V;
int main(){
	ifstream f("pariuri.in");
	int n = 0;
	f >> n;
	int indexPersoane = 0;
	map<int, int> map1;
	long long t = 0, b = 0;
	for (int i = 0; i < n; i++){
		int m = 0; f >> m;
		t = 0, b = 0;
		for (int j = 0; j < m; j++){
			f >> t >> b;
				map1[t]++;
				if (map1[t] == 1){
					V.push_back(t);
				}
			timp[t] += b;
		}
	}
	ofstream o("pariuri.out");
	o << V.size()<<'\n';
	for (int i = 0; i < V.size(); i++){
		o << V[i] << " " << timp[V[i]]<<" ";
	}
	return 0;
}