#include <iostream>
#include<vector>
#include<algorithm>
using namespace std;
struct Activity{
    int start;
    int end;
};
void activitySelection(vector<Activity> act){
    sort(act.begin(),act.end(),[](Activity a,Activity b){
        a.end<b.end;
    });
    cout<<act[0].start<<" , "<<act[0].end<<endl;
    int lastSelected = 0;
    for(int i=1;i<act.size();i++){
        if(act[i].start >= act[lastSelected].end){
            cout<<act[i].start<<" , "<<act[i].end<<endl;
            lastSelected = i;
        }
    }
}
int main() {
    int n;
    cin>>n;

    vector<Activity> act(n);
    
    for(int i=0;i<n;i++){
        cin>>act[i].start>>act[i].end;
    }
    activitySelection(act);
    return 0;
}