#include<cstdio>
int T,n,k,i,j,a[104][104];
bool b[104],v[104];//confirmed,visited
int read(){
	char c;
	while(c=getchar(),c<'0'||c>'9');
	int r=0;
	for(;c>='0'&&c<='9';c=getchar())(r*=10)+=c-'0';
	return r;
}void dfs(int g){
	v[g]=0;
	for(int i=0;i<n;++i)if(v[i]&&a[g][i])dfs(i);
}bool check(int cu,int de){
	if(cu==n||a[de][cu])cu=de;
	b[de]=0;
	for(int i=0;i<n;++i)v[i]=b[i];
	if(b[k])dfs(k);
	b[de]=1;
	if(cu<n)for(int i=0;i<n;++i)if(a[cu][i])v[i]=0;
	for(int i=0;i<n;++i)if(b[i]&&v[i])return 0;
	return 1;
}int main(){
	T=read();
	for(int t=0;t<T;++t){
		n=read();k=read();
		for(i=0;i<n;++i)
		for(j=0;j<n;++j)if(i!=j){
			char c;
			while(c=getchar(),c!='Y'&&c!='N');
			a[i][j]=c=='Y';
		}printf("Case #%d:",t+1);
		for(i=0;i<n;++i)b[i]=1;
		int cur=n;
		if(!check(n,n)){printf(" IMPOSSIBLE");goto end;}
		for(i=0;i<n;++i){
			for(j=0;j<n;++j)
				if(b[j]&&check(cur,j))goto aha;
			aha:b[j]=0;printf(" %d",j);
			if(i==0||a[j][cur])cur=j;
		}end:puts("");
	}return 0;
}