F scs(String x, y)
   I x.empty
      R y
   I y.empty
      R x
   I x[0] == y[0]
      R x[0]‘’scs(x[1..], y[1..])
   I scs(x, y[1..]).len <= scs(x[1..], y).len
      R y[0]‘’scs(x, y[1..])
   E
      R x[0]‘’scs(x[1..], y)

print(scs(‘abcbdab’, ‘bdcaba’))