// #pragma GCC optimize("Ofast")
// #pragma GCC optimize("unroll-loops")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2")
#include <bits/stdc++.h>
// #define int long long
#define i64 long long
#define pii pair <int, int> 
using namespace std;
inline int read(void) {
    int x=0,sgn=1; char ch=getchar();
    while(ch<48||57<ch) {if(ch==45)sgn=0;ch=getchar();}
    while(47<ch&&ch<58) {x=x*10+ch-48;   ch=getchar();}
    return sgn? x:-x;
}
void write(int x) {
    if(x<0) putchar('-'),x=-x;
    if(x>9) write(x/10);
    putchar(x%10+'0');
}
/*
    write((Ans%p+p)%p); pls
*/
int n,tar;
char V[102][102];
vector <int> E[102],res;
bool vis[102];
bool crvis[102];
int que[102],qr;
inline bool check(int st) {
    que[qr=1]=tar;
    memset(crvis,0,sizeof crvis);
    crvis[tar]=1;
    for(int i=1,x; i<=qr; ++i) {
        x=que[i]; 
        if(x!=st&&vis[x]) continue;
        for(int v : E[x]) if(!crvis[v]) crvis[v]=1,que[++qr]=v;
    }
    if(!crvis[st]) return 0;
    for(int i=0; i<n; ++i) if(!(crvis[i]||vis[i])) return 0;
    return 1;
}
inline bool solve(int st) {
    if(!check(st)) return 0;
    if(res.size()==n) return 1;
    for(int i=0; i<n; ++i) if(!vis[i]) {
        vis[i]=1;
        res.push_back(i);
        if(solve(V[st][i]=='Y' ? st :i)) return 1;
        res.pop_back();
        vis[i]=0;
    }
    return 0;
}
inline void work(const int testid) {
    n=read(); tar=read();
    for(int i=0; i<n; ++i) scanf("%s",V[i]);
    for(int i=0; i<n; ++i) E[i].clear();
    for(int i=0; i<n; ++i) {
        for(int u=i+1; u<n; ++u) {
            if(V[i][u]=='Y') E[i].push_back(u);
            else E[u].push_back(i);
        }
    }
    for(int i=0; i<n; ++i) vis[i]=0; 
    res.clear();
    for(int st=0; st<n; ++st) {
        vis[st]=1;
        res.push_back(st);
        if(solve(st)) {
            printf("Case #%d:",testid);
            for(int v : res) putchar(' '),write(v);
            puts("");
            return ;
        }
        res.pop_back();
        vis[st]=0;
    }
    printf("Case #%d:",testid);
    puts(" IMPOSSIBLE");
}
signed main() {
    // freopen("localinput","r",stdin);
    // freopen("localoutput","w",stdout);
    int T=read(); 
    for(int i=1; i<=T; ++i) {
        work(i);
    }
    // fprintf(stderr,"%.4lf\n",1.0*clock()/CLOCKS_PER_SEC);
    return 0;
}