#include <bits/stdc++.h>
const long long int M = 1e9 + 7;
using namespace std;
struct R {
  int x, y;
};
bool cmp(R a, R b) {
  if (a.x != b.x) return a.x < b.x;
  return a.y < b.y;
}
int main() {
  int n, m, i, ii, jj, k, cs = 1, f;
  scanf("%*d");
  while (~scanf("%d", &n)) {
    R a[n + 5];
    string dir = "";
    for (i = 0; i < n; i++) scanf("%d %d", &a[i].x, &a[i].y);
    if (n == 1) {
      for (ii = 0; ii < a[0].x; ii++) dir += 'R';
      for (jj = 0; jj < a[0].y; jj++) dir += 'U';
      cout << "YES\n" << dir << endl;
      continue;
    }
    sort(a, a + n, cmp);
    if (a[1].x < a[0].x || a[1].y < a[1].y) {
      puts("NO");
      continue;
    }
    for (ii = 0; ii < a[0].x; ii++) dir += 'R';
    for (jj = 0; jj < a[0].y; jj++) dir += 'U';
    for (i = 1, f = 0; i < n; i++) {
      if (a[i].x < a[i - 1].x || a[i].y < a[i - 1].y) {
        f = 1;
        break;
      }
      for (; ii < a[i].x; ii++) dir += 'R';
      for (; jj < a[i].y; jj++) dir += 'U';
    }
    if (f)
      puts("NO");
    else
      cout << "YES\n" << dir << endl;
  }
  return 0;
}
