CodeForces

原题链接

import java.util.Scanner;

public class Main{
     public static void main(String[] args){
         Scanner sc = new Scanner(System.in);
         int n = sc.nextInt();
         int[] arr = new int[n+5];
         for(int i=0;i<n;i++) arr[i] = sc.nextInt();
         int res = 0;
         int l = 1;
         for(int i=0;i<n;i++){
             int r = 1;
             int j = i+1;
             while(j<n&&arr[j]==arr[i]){
                 r ++;
                 j ++;
             }
             res = Math.max(res,Math.min(l,r));
             l = r;
             i = j-1;
         }
         System.out.print(res*2);
     }
}