#include <bitset>
#include <vector>
#include <stdio.h>
using namespace std;
bitset<200> v, b[200];
int n, m; vector<int> s; char a[200][200]; 
bool check(const int p)
{
    bitset<200> d, e; d[m] = e[m] = true; int i;
    while ((i = d._Find_first()) < n) { d[i] = false; if (!v[i]) d |= b[i] & ~e, e |= b[i]; }
    if (!e[p]) return false; e |= b[p] | v; return e.count() == n;
}
bool DFS(const int p)
{
    if (~p && !check(p)) return false;
    if (s.size() == n) { for (int i : s) printf("%d ", i); putchar('\n'); return true; }
    for (int i(0); i < n; ++i) if (!v[i])
    {
        v[i] = true; s.emplace_back(i);
        if (DFS(~p && b[p][i] ? p : i)) return true;
        v[i] = false; s.pop_back();
    }
    return false;
}
int main()
{
    int t; scanf("%d", &t); for (int c(1); c <= t; ++c) {
        scanf("%d%d", &n, &m);
        for (int i(0); i < n; ++i)
        {
            b[i].reset(); scanf("%s", a[i]);
            for (int j(0); j < n; ++j) if (a[i][j] == 'Y') b[i][j] = true;
        }
        printf("Case #%d: ", c); v.reset();
        if (DFS(-1)) s.clear(); else puts("IMPOSSIBLE");
    } return 0;
}