// CONTEST SOURCE
#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cstdio>
#include <vector>
#include <cmath>
#include <algorithm>
#include <map>
#include <queue>
#include <set>
#include <climits>
//#include <priority_queue>
using namespace std;
#define ll long long
#define x first
#define y second
#define pii pair<int, int>
#define pdd pair<double, double>
#define L(s) (int)(s).size()
#define VI vector<int>
#define all(s) (s).begin(), (s).end()
#define pb push_back
#define mp make_pair
#define inf 1000000000
int t, n, p, q, r, pq, qr, rp;
int e[6][6];
char path[1111];
int ptr;
void dfs(int v) {
  for(int j = 0; j < 6; ++j) {
    while(e[v][j]) {
      --e[v][j];
      dfs(j);
    }
  }
  if (v == 0) path[ptr++] = 'R'; else
    if (v == 1) path[ptr++] = 'Y'; else
      if (v == 2) path[ptr++] = 'B'; else
        if (v == 3) path[ptr++] = 'G'; else
          if (v == 4) path[ptr++] = 'V'; else
            if (v == 5) path[ptr++] = 'O';
}
bool solve() {
    if (p < qr || q < rp || r < pq) return 0;
    for(int p2q = 0; p2q <= p - qr && p2q <= q - rp; ++p2q) {
      e[0][3] = qr;
      e[3][0] = qr;
      e[1][4] = rp;
      e[4][1] = rp;
      e[2][5] = pq;
      e[5][2] = pq;

      e[0][1] = p2q;
      e[0][2] = p - e[0][3] - e[0][1];
      e[2][1] = q - e[0][1] - e[4][1];
      e[2][0] = r - e[2][5] - e[2][1];
      e[1][2] = r - e[0][2] - e[5][2];
      e[1][0] = p - e[3][0] - e[2][0];

      if (e[0][2] < 0 || e[2][1] < 0 || e[2][0] < 0 || e[1][2] < 0 || e[1][0] < 0) continue;
      if (e[0][1] + e[0][2] + e[0][3] != p) continue;
      if (e[1][0] + e[2][0] + e[3][0] != p) continue;
      if (e[1][0] + e[1][2] + e[1][4] != q) continue;
      if (e[0][1] + e[2][1] + e[4][1] != q) continue;
      if (e[2][0] + e[2][1] + e[2][5] != r) continue;
      if (e[0][2] + e[1][2] + e[5][2] != r) continue;

      int idx = 0; while(e[idx][0] + e[idx][1] + e[idx][2] == 0) ++idx;

      ptr = 0;
      dfs(idx);

      if (ptr != n + 1) continue;
      path[n] = 0;
      return 1;
    }
    return 0;
}
int main() {
  freopen("B-small-attempt0.in", "r", stdin);
  freopen("output.txt", "w", stdout);
  cin >> t;
  for(int tc = 1; tc <= t; ++tc) {
    cerr << tc << endl;
    cin >> n;
    cin >> p >> pq >> q >> qr >> r >> rp;
    cout << "Case #" << tc << ": ";
    if (!solve()) cout << "IMPOSSIBLE\n";
    else cout << path << endl;
  }
}