dbl
0
0
dbl
s
X
s
s
dbl
X
dbls
nil
nil
dbls
cons
X
Y
cons
dbl
X
dbls
Y
sel
0
cons
X
Y
X
sel
s
X
cons
Y
Z
sel
X
Z
indx
nil
X
nil
indx
cons
X
Y
Z
cons
sel
X
Z
indx
Y
Z
from
X
cons
X
from
s
X
2.2
sel
s
X
cons
Y
Z
sel
X
Z
dbls
cons
X
Y
dbl
X
dbls
cons
X
Y
dbls
Y
indx
cons
X
Y
Z
indx
Y
Z
from
X
from
s
X
dbl
s
X
dbl
X
indx
cons
X
Y
Z
sel
X
Z
true
from
X
from
s
X
true
Failed!
NaTT
certifiable-1.6