f=(b,c=j=(l=b.replace(/\n/g,r='')).length)=>[...b].map(d=>{for(a=t=9;a;)t-='H'!=l[(0|j-1+(--a%3-1)*b.search`
`+a/3)%c];j+=`
`!=d,r+={H:'t',t:'.','.':t&&3>t&&'H'}[d]||d})&&r