#include <bits/stdc++.h>   using namespace std;   const long long mod = 1000000007;   const long long inf = 1000000000000000000;   int main() {     long long t;     cin >> t;     while (t--) {       long long n;       cin >> n;       vector<pair<long long, long long> > p(n);       for (auto& x : p) cin >> x.first >> x.second;       sort(p.begin(), p.end());       pair<long long, long long> now = {0, 0};       bool f = 1;       string ans =   ;       for (int i = 0; i < n; i++) {         if (p[i].first >= now.first && p[i].second >= now.second) {           long long r = p[i].first - now.first, u = p[i].second - now.second;           while (r--) ans +=  R ;           while (u--) ans +=  U ;           now = p[i];         } else {           f = 0;           break;         }       }       if (f)         cout <<  YES n  << ans << endl;       else         cout <<  NO n ;     }     return 0;   }   