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| 1 | +```java |
| 2 | +import java.io.BufferedReader; |
| 3 | +import java.io.IOException; |
| 4 | +import java.io.InputStreamReader; |
| 5 | +import java.util.ArrayList; |
| 6 | +import java.util.Arrays; |
| 7 | +import java.util.Collections; |
| 8 | +import java.util.HashMap; |
| 9 | +import java.util.HashSet; |
| 10 | +import java.util.LinkedList; |
| 11 | +import java.util.PriorityQueue; |
| 12 | +import java.util.Queue; |
| 13 | +import java.util.StringTokenizer; |
| 14 | + |
| 15 | +public class Main { |
| 16 | + |
| 17 | + static int[][] dp = new int[10001][500]; |
| 18 | + static HashSet<Integer> set = new HashSet<>(); |
| 19 | + static int total,setSize,ans; |
| 20 | + |
| 21 | + |
| 22 | + public static void main(String[] args) throws IOException { |
| 23 | + init(); |
| 24 | + process(); |
| 25 | + print(); |
| 26 | + |
| 27 | + |
| 28 | + } |
| 29 | + |
| 30 | + private static void init() throws IOException{ |
| 31 | + BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); |
| 32 | + StringTokenizer st = new StringTokenizer(br.readLine()); |
| 33 | + total = Integer.parseInt(st.nextToken()); |
| 34 | + setSize = Integer.parseInt(st.nextToken()); |
| 35 | + for (int i = 0; i < setSize; i++) { |
| 36 | + set.add(Integer.parseInt(br.readLine())); |
| 37 | + } |
| 38 | + for (int i = 0; i <= 10000; i++) { |
| 39 | + Arrays.fill(dp[i], Integer.MAX_VALUE); |
| 40 | + } |
| 41 | + |
| 42 | + |
| 43 | + } |
| 44 | + |
| 45 | + private static void process() throws IOException { |
| 46 | + if (set.contains(2)) { |
| 47 | + ans = -1; |
| 48 | + return; |
| 49 | + } |
| 50 | + dp[2][1] = 1; |
| 51 | + for (int i = 2; i< total; i++) { |
| 52 | + if (set.contains(i)) continue; |
| 53 | + for (int j = 1; j < 500; j++) { |
| 54 | + if (dp[i][j] == Integer.MAX_VALUE) continue; |
| 55 | + |
| 56 | + int more = j+1; |
| 57 | + int less =j-1; |
| 58 | + if (more < 500 && i+more <= total && !set.contains(i+more)) { |
| 59 | + dp[i+more][more] = Math.min(dp[i+more][more], dp[i][j]+1); |
| 60 | + } |
| 61 | + if (j < 500 && i+j <= total && !set.contains(i+j)) { |
| 62 | + dp[i+j][j] = Math.min(dp[i+j][j], dp[i][j]+1); |
| 63 | + } |
| 64 | + if (less != 0 && i+less <=total && !set.contains(i+less)) { |
| 65 | + dp[i+less][less] = Math.min(dp[i+less][less], dp[i][j]+1); |
| 66 | + } |
| 67 | + } |
| 68 | + } |
| 69 | + |
| 70 | + ans = Integer.MAX_VALUE; |
| 71 | + for (int i = 1; i < 500; i++) { |
| 72 | + ans = Math.min(ans, dp[total][i]); |
| 73 | + } |
| 74 | + if (ans == Integer.MAX_VALUE) ans = -1; |
| 75 | + |
| 76 | + } |
| 77 | + |
| 78 | + |
| 79 | + private static void print() { |
| 80 | + System.out.print(ans); |
| 81 | + } |
| 82 | + |
| 83 | +} |
| 84 | +``` |
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