#include <fstream>
using namespace std;
ifstream fin("date.in");
ofstream fout("date.out");
struct interval
{
    double a,b;
};
int n;
interval X[100];
int main()
{
    int i,j;
    interval aux;
    float xr,yr;
    fin>>n;
    for(i=1;i<=n;i++) fin>>X[i].a>>X[i].b;
    for(i=1;i<n;i++)
        for(j=i+1;j<=n;j++)
            if(X[i].b>X[j].b)
            {
                aux=X[i]; X[i]=X[j]; X[j]=aux;
            }
    xr=X[1].a; yr=X[1].b;
    for(i=2;i<=n;i++)
        if(X[i].a<yr)
            {
                if(X[i].a<xr) xr=X[i].a;
                yr=X[i].b;
            }
        else
        {
            fout<<"("<<xr<<","<<yr<<") U ";
            xr=X[i].a;
            yr=X[i].b;
        }
    fout<<"("<<xr<<","<<yr<<") ";
    fout.close();
    fin.close();
    return 0;
}