import java.util.Random;
import java.lang.Math;
public class Main{
    public static void main(String[] args){
        int x=0;
        double result=0;
        for(int i=0;i<100000;i++) {
            x = change(x);
            result =result+( x / 4);
        }
        System.out.print(result/100000);
    }
        public static int change(int x){
            int[] sum = new int[52];
            int[] data = {1,2,3,4,5,6,7,8,9,10,11,12,13,
                    1,2,3,4,5,6,7,8,9,10,11,12,13,
                    1,2,3,4,5,6,7,8,9,10,11,12,13,
                    1,2,3,4,5,6,7,8,9,10,11,12,13};//撲克牌
 
            Random r = new Random();
            int[] array = new int[52];
for (int i=0; i<52; i++){
                array[i] = r.nextInt(52);
                for (int j=0; j<i;){
                    if (array[j]==array[i]){
                        array[i] = r.nextInt(52);
                        j=0;
                    }
                    else j++;
                }
            }
 
            for(int i=0;i<52;i++){
                sum[i]=data[array[i]];
            }//將撲克牌的順序打亂
            int count=0;//蓋牌次數
            int t = 0;//牌的位置
            for(int m=0;m<4;m++) {
                for (int i = 10; i > 0; i--) {
                    if (sum[t + 10 - i] == i) {
                        t = t + 10 - i + 1;
                        break;
                    } else if (sum[t+9] != 1 && i == 1) {
                        count++;
                        t = t + 11;//蓋牌
                    }
                }
            }
            x=count;
            return x;
        }
    }

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