Problem:
Score : 300 points

Problem Statement

There are N people numbered 1 to N. Each of them is either an honest person whose testimonies are always correct or an unkind person whose testimonies may be correct or not.

Person i gives A_i testimonies. The j-th testimony by Person i is represented by two integers x_{ij} and y_{ij}. If y_{ij} = 1, the testimony says Person x_{ij} is honest; if y_{ij} = 0, it says Person x_{ij} is unkind.

How many honest persons can be among those N people at most?

Constraints

All values in input are integers.

1 \leq N \leq 15

0 \leq A_i \leq N - 1

1 \leq x_{ij} \leq N

x_{ij} \neq i

x_{ij_1} \neq x_{ij_2} (j_1 \neq j_2)

y_{ij} = 0, 1

Input

Input is given from Standard Input in the following format:

N
A_1
x_{11} y_{11}
x_{12} y_{12}
:
x_{1A_1} y_{1A_1}
A_2
x_{21} y_{21}
x_{22} y_{22}
:
x_{2A_2} y_{2A_2}
:
A_N
x_{N1} y_{N1}
x_{N2} y_{N2}
:
x_{NA_N} y_{NA_N}

Output

Print the maximum possible number of honest persons among the N people.

Sample Input 1

3
1
2 1
1
1 1
1
2 0

Sample Output 1

2

If Person 1 and Person 2 are honest and Person 3 is unkind, we have two honest persons without inconsistencies, which is the maximum possible number of honest persons.

Sample Input 2

3
2
2 1
3 0
2
3 1
1 0
2
1 1
2 0

Sample Output 2

0

Assuming that one or more of them are honest immediately leads to a contradiction.

Sample Input 3

2
1
2 0
1
1 0

Sample Output 3

1

Solution in OCaml (4.02.3) (judge verdict: Accepted)

let popcnt x =
  let x = (x land 0x5555555555555555) + ((x lsr 1) land 0x5555555555555555) in
  let x = (x land 0x3333333333333333) + ((x lsr 2) land 0x3333333333333333) in
  let x = (x land 0x0f0f0f0f0f0f0f0f) + ((x lsr 4) land 0x0f0f0f0f0f0f0f0f) in
  let x = (x land 0x00ff00ff00ff00ff) + ((x lsr 8) land 0x00ff00ff00ff00ff) in
  let x = (x land 0x0000ffff0000ffff) + ((x lsr 16) land 0x0000ffff0000ffff) in
  (x land 0x00000000ffffffff) + ((x lsr 32) land 0x00000000ffffffff)


let () = Scanf.scanf "%d\n" @@ fun n ->
  let xyss =
    Array.init n @@ fun _ ->
      Scanf.scanf "%d\n" @@ fun a ->
        Array.to_list @@ Array.init a @@ fun _ ->
          Scanf.scanf "%d %d\n" @@ fun x y -> x, y in
  Printf.printf "%d\n" @@
  Array.fold_left max min_int @@
  Array.init (1 lsl n) @@ fun ans ->
    if
      Array.fold_left ( && ) true @@
      Array.init n @@ fun i ->
        if ans land (1 lsl i) = 0
        then true
        else
          List.for_all (fun (x, y) ->
            ans land (1 lsl (x - 1)) = y lsl (x - 1)) xyss.(i)
    then popcnt ans
    else 0