Lipton_6

#include<iostream>
#include<set>
#include<iomanip>
#include<algorithm>
#include<vector>

using namespace std;

int main(){
    int t, n, x, y, f;
    vector<pair<int, int> > v;
    vector<char> res;
    cin >> t;
    for(int tc = 0; tc < t; tc++){
        cin >> n;
        v.clear();
        res.clear();
        for(int i = 0; i < n; i++){
            cin >> x >> y;
            v.push_back({x, y});
        }
        sort(v.begin(), v.end(),
             [](pair<int, int> a, pair<int, int> b){
                 if(a.second == b.second){
                    return a.first < b.first;
                 }
                 return a.second < b.second;
             });
        x = 0;
        y = 0;
        f = 1;
        for(int i = 0; i < (int)v.size(); i++){
           if(v[i].first < x || v[i].second < y){
                cout << "NO\n";
                f = 0;
                break;
            }
            for(; x < v[i].first; x++){
                res.push_back('R');
            }
            for(; y < v[i].second; y++){
                res.push_back('U');
            }
        }
        if(f){
            cout << "YES\n";
            for(int i = 0; i < (int)res.size(); i++){
                cout << res[i];
            }
            cout << "\n";
        }
    }
    return 0;
}