#include<bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define uint unsigned int
#define ldb long double
#define pii pair<int,int>
#define mkp make_pair
#define mkt make_tuple
#define fr first
#define se second
#define uset unordered_set
#define umap unordered_map
#define pqueue priority_queue
#define all(_box) _box.begin(),_box.end()
#define ppc __builtin_popcount
#define ctz __builtin_ctz
#define clz __builtin_clz
#define lbd lower_bound
#define ubd upper_bound
#define deb(x) cerr<<#x<<'='<<(x)<<' '
using namespace std;
const int N=104;
int n,s,cnt;
string mp[N];
bool vis[N],used[N];

void dfs(int u){
    for(int v=0;v<n;v++){
        if(vis[v]||used[v]||mp[u][v]!='Y')continue;
        vis[v]=1,dfs(v);
    }
}
void solve(){
    cin>>n>>s;
    for(int i=0;i<n;i++)cin>>mp[i];
    memset(vis,0,sizeof(vis));
    memset(used,0,sizeof(used));
    vis[s]=1,dfs(s);
    if(count(vis,vis+n,0)){
        cout<<"IMPOSSIBLE\n";
        return;
    }

    int lst=-1;
    for(int i=0;i<n;i++){
        for(int j=0;j<n;j++)if(!used[j]){
            if(j==s){
                if(lst!=-1&&mp[s][lst]!='Y')continue;
                bool skp=0;
                used[j]=1;
                for(int k=0;k<n;k++)
                    if(!used[k]&&mp[s][k]!='Y')skp=1;
                used[j]=0;
                if(skp)continue;
                lst=s;
            }
            else if(!used[s]){
                memset(vis,0,sizeof(vis));
                used[j]=1;
                vis[s]=1,dfs(s);
                int cur=lst;
                if(lst==-1||mp[j][lst]=='Y')cur=j;
                bool skp=0;
                for(int k=0;k<n;k++)
                    if(!used[k]&&!vis[k]&&mp[cur][k]!='Y')skp=1;
                used[j]=0;
                if(skp)continue;
                lst=cur;
            }
            used[j]=1;
            cout<<j<<' ';
            break;
        }
    }
    cout<<'\n';
}
int main(){
    ios::sync_with_stdio(0);
    cin.tie(0),cout.tie(0);

    int T;
    cin>>T;
    for(int i=1;i<=T;i++){
        cout<<"Case #"<<i<<": ";

        solve();
    }
}