procedure main(A)
   s1 := \A[1] | "thisisatest"
   s2 := \A[2] | "testing123testing"
   write(s1)
   write(s2)
   write("---")
   write(lcs(s1,s2))
end

procedure lcs(s1,s2)
   lc := ""
   s1 ? every (tab(upto(s2)), c1 := move(1), cs:="") do {
           while p2 := upto(c1, s2) do
              while (c1 == s2[p2]) | break break do
                 (cs ||:= c1, p2 +:= 1, c1 := move(1))
           if *cs > *lc then lc := cs
           }
   return lc
end