k
1
2
3
4
5
6
7
8
9
a
1
a
2
a
3
a
4
a
5
+
a
3
a
4
a
5
+
a
1
a
4
a
5
+
a
1
a
2
a
5
+
a
1
a
2
a
3
+
a
5
+
a
3
+
a
1