<s>
In	O
computer	B-General_Concept
science	I-General_Concept
,	O
the	O
shortest	B-Algorithm
common	I-Algorithm
supersequence	I-Algorithm
of	O
two	O
sequences	O
X	O
and	O
Y	O
is	O
the	O
shortest	O
sequence	O
which	O
has	O
X	O
and	O
Y	O
as	O
subsequences	O
.	O
</s>
<s>
A	O
shortest	B-Algorithm
common	I-Algorithm
supersequence	I-Algorithm
(	O
SCS	O
)	O
is	O
a	O
common	O
supersequence	O
of	O
minimal	O
length	O
.	O
</s>
<s>
In	O
the	O
shortest	B-Algorithm
common	I-Algorithm
supersequence	I-Algorithm
problem	I-Algorithm
,	O
two	O
sequences	O
X	O
and	O
Y	O
are	O
given	O
,	O
and	O
the	O
task	O
is	O
to	O
find	O
a	O
shortest	O
possible	O
common	O
supersequence	O
of	O
these	O
sequences	O
.	O
</s>
<s>
By	O
inserting	O
the	O
non-LCS	O
symbols	O
into	O
Z	O
while	O
preserving	O
their	O
original	O
order	O
,	O
we	O
obtain	O
a	O
shortest	B-Algorithm
common	I-Algorithm
supersequence	I-Algorithm
U	O
.	O
</s>
<s>
There	O
is	O
no	O
similar	O
relationship	O
between	O
shortest	B-Algorithm
common	I-Algorithm
supersequences	I-Algorithm
and	O
longest	O
common	O
subsequences	O
of	O
three	O
or	O
more	O
input	O
sequences	O
.	O
</s>
