#include <iostream>
#include <fstream>
#include <unordered_map>
using namespace std;

ifstream f("pariuri.in");
ofstream g("pariuri.out");

int n,m,i,j,max1;
long a,b;
//long v[30000];

unordered_map <int,int> ump;
unordered_map <int,int> ump1;
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(NULL);
    max1=-100000;
    f>>n;
    g<<n<<endl;
    for(i=1;i<=n;i++)
    {
        f>>m;
        for(j=1;j<=m;j++)
        {
            f>>a>>b;
            ump[a]+=b;
            ump1[a]=1;
            if(a>max1)
                max1=a;
        }
    }
    /*
    for(auto i = ump.begin();i!=ump.end();i++)
        cout<<(*i).first;
        */
    for(i=1;i<=max1;i++)
        if(ump1[i]==1)
        g<<i<<" "<<ump[i]<<" ";
    return 0;
}