#! /usr/bin/gawk -f
BEGIN{
    while((getline < "/home/adav/cities")==1){
    a[len++]=$0;print len,$0
    }
    close("/home/adav/cities");
    max=0;
}

function try(i,       s,lvl,j,found){
   b[i]=1;
    found=0;
    for(j=0;j<len;j++){
    if((substr(a[i],length(a[i]),1)==substr(a[j],1,1))&&
       !b[j]){
        found=1;
        try(j,s ", " a[i],lvl+1);
    }
    }
  b[i]=0;
  if(!found)if((lvl>=max)) {max=lvl;
      print lvl+1, s ", " a[i];
      }
}
END{
    for(z=0;z<len;z++)try(z,"",0);
}