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| 1 | +```java |
| 2 | + |
| 3 | +import java.io.BufferedReader; |
| 4 | +import java.io.IOException; |
| 5 | +import java.io.InputStreamReader; |
| 6 | +import java.util.*; |
| 7 | + |
| 8 | +public class Main { |
| 9 | + |
| 10 | + static BufferedReader br= new BufferedReader(new InputStreamReader(System.in)); |
| 11 | + static int problemCnt, studentCnt; |
| 12 | + static int goal,ans = -1; |
| 13 | + static int[] arr,comb; |
| 14 | + |
| 15 | + |
| 16 | + public static void main(String[] args) throws NumberFormatException, IOException { |
| 17 | + init(); |
| 18 | + process(); |
| 19 | + print(); |
| 20 | + |
| 21 | + } |
| 22 | + |
| 23 | + |
| 24 | + |
| 25 | + public static void init() throws NumberFormatException, IOException { |
| 26 | + StringTokenizer st = new StringTokenizer(br.readLine()); |
| 27 | + problemCnt = Integer.parseInt(st.nextToken()); |
| 28 | + studentCnt = Integer.parseInt(st.nextToken()); |
| 29 | + arr = new int[studentCnt]; |
| 30 | + comb = new int[studentCnt]; |
| 31 | + |
| 32 | + goal = ( 1 << problemCnt)-1; |
| 33 | + |
| 34 | + for (int i = 0; i < studentCnt; i++) { |
| 35 | + st = new StringTokenizer(br.readLine()); |
| 36 | + int num = 0 ; |
| 37 | + int numCnt = Integer.parseInt(st.nextToken()); |
| 38 | + for (int j = 0 ; j < numCnt; j++) { |
| 39 | + num += (1 << (Integer.parseInt(st.nextToken())-1)); |
| 40 | + } |
| 41 | + arr[i] = num; |
| 42 | + } |
| 43 | + } |
| 44 | + |
| 45 | + public static void process() throws IOException { |
| 46 | + for (int size = 1; size <= studentCnt; size++) { |
| 47 | + combination(size, 0,0); |
| 48 | + |
| 49 | + if (ans == size) return; |
| 50 | + } |
| 51 | + } |
| 52 | + |
| 53 | + public static void combination(int size, int idx, int cnt) { |
| 54 | + if (size == cnt) { |
| 55 | + int res = 0; |
| 56 | + |
| 57 | + for (int i = 0; i < size; i++) { |
| 58 | + res |= comb[i]; |
| 59 | + } |
| 60 | + if (res == goal) { |
| 61 | + ans = size; |
| 62 | + } |
| 63 | + return; |
| 64 | + } |
| 65 | + |
| 66 | + for (int i = idx; i < studentCnt; i++) { |
| 67 | + comb[cnt] = arr[i]; |
| 68 | + combination(size,i+1,cnt+1); |
| 69 | + } |
| 70 | + } |
| 71 | + |
| 72 | + |
| 73 | + |
| 74 | + |
| 75 | + public static void print() { |
| 76 | + System.out.print(ans); |
| 77 | + |
| 78 | + } |
| 79 | +} |
| 80 | +``` |
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