nds:=File("daysOfWeek.txt").read().howza(11)	// stripped lines
.pump(List,Void.Filter,fcn(day){
   d,N,m := day.split(),d.len(),(0).max(d.apply("len"));  // N==7
   foreach n in ([1..m]){
      ds:=d.apply("get",0,n);  // ("Su","Mo","Tu","We","Th","Fr","Sa")
      foreach a,b in (N,[a+1..N-1]){ if(ds[a]==ds[b]) continue(3); } # Th==Fr?
      return(n,day);	// part way though the words and found unique
   }
   return(m,day); // no match nowhere
});
foreach n,s in (nds){ println("%3d  %s".fmt(n,s)); }