#include <bits/stdc++.h>

using namespace std;

vector<pair<int, int>> boxes;

int main()
{
    int n,t;
    cin >> t;
    for(int i = 0; i < t; i++)
    {
        cin >> n;
        int c=0,pas=0,ok=0;
        boxes.clear();
        for(int j = 0; j < n; j++)
        {
            int x,y;
            cin >> x >> y;
            boxes.push_back({x, y});
        }
        sort(boxes.begin(), boxes.end());
        int xcutie=boxes[i].first, ycutie=boxes[i].second;
        do
        {
            if (xcutie)
            {
                xcutie++;
                c++;
                ok=1;
            }
            if (ycutie)
            {
                ycutie++;
                c++;
                ok=1;
            }
            pas++;

        }while (c==n || pas>=n*n);
        if (!ok)
        {
            cout<<"NO"<<endl;
        }
        else
        {
            cout<<"YES"<<endl;
         xcutie=boxes[i].first;
        ycutie=boxes[i].second;
         do
        {
            if (xcutie)
            {
                xcutie++;
                c++;
                cout<<"U";
            }
            if (ycutie)
            {
                ycutie++;
                c++;
                cout<<"R";
            }
        }while (c==n);
        }
        cout<<endl;
    }
    return 0;
}