/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static double p(int x)
	{
		double r = 1.0;
		for (int i = 2; i <= x; i++) r *= i;
		return r;
	}
	public static void main (String[] args) throws java.lang.Exception
	{
		// your code goes here
		Scanner s = new Scanner(System.in);
		int n = s.nextInt();
		if (n > 50 || n < 0)
		{
			System.out.println("不在范围！");
		}
		else
		{
			double d = 0;
			for (int i = 1; i <= n; i++)
				d += p(i);
			System.out.println("结果=" + d);
		}
	}
}

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NA==

4