How many books in the Heroes of Olympus series?
6
5
5
5
5
5
5
5
6
7
5
6
7
5
4
6
7
5
4
6
7
5
3
4
6
7
5
3
4
6
7
5
3
4
6
7
5
3
4
6
7
5
3
4
6
7
5
3
4
6
7
5
3
4
6
7
5
3
4
6
7
5
3
4
6
7
5
3
4
8
6
7
3
4
8
6
7
3
4
8
6
7
3
4
8
6
7
3
4
8
6
7
3
4
8
6
7
3
4
8
1
6
7
3
4
8
1
3
4
8
1
9
3
8
1
9
10
3
8
1
9
ten
10
12
8
1
9
10
12
14
8
1
9
10
2
12
14
8
0
1
9
10
2
12
14
8
1
9
10
11
2
12
14
8
1
9
10
11
2
13
12
14
8
1
9
10
11
2
13
12
14
8
1
9
10
11
2
13
12
14
8
1
9
10
11
2
13
12
14
8
1
9
10
11
2
13
12
14
1
148
58