import java.util.*;
import java.lang.*;
 
class Main
{
    public static void main (String[] args) throws java.lang.Exception {
        System.out.println(P(3, 10));
    }
 
    public static double P(int dice, int r) {
        if (dice == 0) {
            // Zero dice: probabiliy 1 to get 0
            if (r == 0) {
                return 1.0;
            } else {
                return 0.0;
            }
        } else {
            // Multiple dice: recursion
            double sum = 0.0;
            for (int i = r - 6; i < r; i++) {
                sum += P(dice - 1, i) / 6.0;
            }
            return sum;
        }
    }
}

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