def subset(A;B):
# TCO
def _subset:
if .[0]|length == 0 then true
elif .[1]|length == 0 then false
elif .[0][0] == .[1][0] then [.[0][1:], .[1][1:]] | _subset
elif .[0][0] < .[1][0] then false
else [ .[0], .[1][1:] ] | _subset
end;
[A,B] | _subset;