How many Dark Tower series are there?
9
3
3
3
2
3
2
3
2
4
3
2
4
5
3
2
4
5
1
3
2
4
5
1
3
2
4
5
1
3
2
4
5
1
3
2
4
5
1
3
2
4
5
1
3
2
4
5
1
3
2
4
5
1
3
6
2
4
5
1
3
6
2
4
5
1
3
7
6
2
4
5
1
3
7
6
2
4
5
1
3
7
6
2
4
5
1
3
7
6
2
4
5
1
7
6
2
4
5
1
7
6
2
4
5
1
7
6
8
4
5
1
7
6
8
4
5
1
7
6
8
5
1
7
6
8
1
7
6
8
9
7
6
8
9
10
7
13
6
8
11
9
10
7
13
6
8
11
9
10
7
13
6
8
12
11
9
10
7
13
6
8
12
11
9
10
7
13
6
8
12
11
9
10
7
13
6
8
12
11
9
10
7
13
8
12
11
9
10
7
13
8
14
12
3 series
2 series
4 series
3 series
128
112
7 series