Problem:
 Score : 500 points    Problem Statement We have N locked treasure boxes, numbered 1 to N .  A shop sells M keys. The i -th key is sold for a_i yen (the currency of Japan), and it can unlock b_i of the boxes: Box c_{i1} , c_{i2} , ... , c_{i{b_i}} . Each key purchased can be used any number of times.  Find the minimum cost required to unlock all the treasure boxes. If it is impossible to unlock all of them, print -1 .      Constraints  All values in input are integers.  1 \leq N \leq 12  1 \leq M \leq 10^3  1 \leq a_i \leq 10^5  1 \leq b_i \leq N  1 \leq c_{i1} < c_{i2} < ... < c_{i{b_i}} \leq N         Input Input is given from Standard Input in the following format:  N  M  a_1  b_1  c_{11}  c_{12}  ...  c_{1{b_1}}  :  a_M  b_M  c_{M1}  c_{M2}  ...  c_{M{b_M}}       Output Print the minimum cost required to unlock all the treasure boxes.
If it is impossible to unlock all of them, print -1 .        Sample Input 1 2 3
10 1
1
15 1
2
30 2
1 2      Sample Output 1 25  We can unlock all the boxes by purchasing the first and second keys, at the cost of 25 yen, which is the minimum cost required.       Sample Input 2 12 1
100000 1
2      Sample Output 2 -1  We cannot unlock all the boxes.       Sample Input 3 4 6
67786 3
1 3 4
3497 1
2
44908 3
2 3 4
2156 3
2 3 4
26230 1
2
86918 1
3      Sample Output 3 69942

Solution (Python):
import sys
n, m = map(int, input().split())
keys = []
box = [[] for _ in range(n+1)]

dr = 2**n
dp = [-1] * dr
dp[0] = 0

for i in range(m):
    a, b = map(int, sys.stdin.readline().split())
    c = list(map(int, sys.stdin.readline().split()))
    k = 0
    for box in c:
        k += 1 << box-1
    for j in range(dr):
        if dp[j] != -1:
            price = dp[j] + a
            nex = j | k
            if dp [nex] == -1 or dp[nex] > price:
                dp[nex] = price

print(dp[dr-1])