#pragma GCC optimize("Ofast","inline","-ffast-math")
#pragma GCC target("avx,sse2,sse3,sse4,mmx")
#include <bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/hash_policy.hpp>
//#define int long long
using namespace __gnu_pbds;
using namespace std;

struct custom_hash {
    static uint64_t splitmix64(uint64_t x) {
        x += 0x9e3779b97f4a7c15;
        x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
        x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
        return x ^ (x >> 31);
    }

    size_t operator()(uint64_t x) const {
        static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
        return splitmix64(x + FIXED_RANDOM);
    }
};

int n,X,vis[110],used[110],bad[110],ans[110],ok[110][110];
vector<int> v[110];

inline void dfs(int x,int y)
{
	used[x]=1;
	if(x==y) return;
	for(int i=0;i<(int)v[x].size();i++) if(!bad[v[x][i]]&&!used[v[x][i]]){
		dfs(v[x][i],y);
	}
}

signed main()
{
	ios::sync_with_stdio(false);cin.tie(0);
	int t;cin>>t;
	int tot=0;
	while(t--){
		cin>>n>>X;X++;tot++;
		for(int i=1;i<=n;i++) v[i].clear(),vis[i]=0,bad[i]=0,ans[i]=0;
		for(int i=1;i<=n;i++) for(int j=1;j<=n;j++) ok[i][j]=0;
		for(int i=1;i<=n;i++){
			for(int j=1;j<=n;j++){
				char ch;cin>>ch;
				if(ch=='Y'){
					ok[i][j]=1;
					v[i].push_back(j);
				}
			}
		}
		bool flag=true;
		int p=-1;
		for(int i=1;i<=n;i++){
			int pos=-1;
			for(int j=1;j<=n;j++) if(!vis[j]){
				int u=j;
				if(i>1&&ok[p][j]) u=p;
				if(i>1){
					if(u==p) bad[j]=1;
					else bad[p]=1;
				}
				if(bad[X]){
					if(i>1){
						if(u==p) bad[j]=0;
						else bad[p]=0;
					}
					continue;
				}
				for(int k=1;k<=n;k++) used[k]=0;
				dfs(X,u);
				bool now=true;
				for(int k=1;k<=n;k++) if(!bad[k]&&!used[k]){
					if(!ok[u][k]){
						now=false;break;
					}
				}
				if(i>1){
					if(u==p) bad[j]=0;
					else bad[p]=0;
				}
				if(now){
					pos=j;break;
				}
			}
			if(pos==-1){
				flag=false;break;
			}
			ans[i]=pos;vis[pos]=1;
			if(i==1) p=ans[i];
			else{
				if(ok[p][ans[i]]) bad[ans[i]]=1;
				else bad[p]=1,p=ans[i];
			}
		}
		cout<<"Case #"<<tot<<": ";
		if(!flag) cout<<"IMPOSSIBLE\n";
		else{
			for(int i=1;i<=n;i++) cout<<ans[i]-1<<' ';
			cout<<'\n';
		}
	}
	return 0;
}