#include<bits/stdc++.h>
#define N 110
#define For(i,a,b) for(register int i=a;i<=b;i++)
using namespace std;
int n,e[N][N],a[N],en;
bool ban[N],vis[N],mark[N];
char s[N][N];
inline void dfs(int x)
{
    mark[x]=true;
    For(i,1,n) if(!mark[i] && e[x][i]) dfs(i);
    return;
}

inline bool check(int x,int y)
{
    x=e[x][y]?x:y;
    For(i,0,n) mark[i]=ban[i];
    mark[x]=true;
    if(mark[en] && x != en) return false;
    if(!mark[en]) 
    {
        dfs(en);
        For(i,1,n) if(!mark[i] && !e[x][i]) return false;
    }
    return true;
}

int main()
{
    int T;scanf("%d",&T);
    For(test,1,T)
    {
        scanf("%d%d",&n,&en),en++;
        memset(e,false,sizeof(e));
        For(i,1,n) scanf("%s",s[i]+1);
        For(i,1,n) For(j,i+1,n)
            if(s[i][j] == 'Y') e[i][j]=true;
            else e[j][i]=true;
        memset(ban,false,sizeof(ban));
        printf("Case #%d: ",test);
        if(!check(0,0)) {printf("IMPOSSIBLE\n");continue;}
        for(int lst=0,i=1;i<=n;i++)
            For(j,1,n) if(!ban[j] && check(lst,j))
            {
                ban[j]=true,printf("%d ",j-1);
                lst=j;break;
            }
        printf("\n");
    }
    return 0;
}