/* 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 void main (String[] args) throws java.lang.Exception
	{
		System.out.println(Silnia(100));
	}
 
	static public double Silnia(double ekran)
    {
        if (ekran == 0) 
            return 1;
        else 
            return ekran * Silnia(ekran - 1);
    }
}

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