import java.util.Scanner;

 import java.lang.*;

 public class cjava {

      public static void main(String[] args) {

          double x1,x2,f1,f2,x;

          Scanner a=new Scanner(System.in);

          do

          {

              System.out.println("input x1,x2:");

             x1=a.nextDouble();

             x2=a.nextDouble();

             f1=f(x1);

             f2=f(x2);

         }while(f1*f2>=0);

         x=root(x1,x2);

        System.out.println("A root of equation is "+x);

     }

     static double f(double x) {

         double y;

         y=x*x-5*x+16*x-80;

       return y;

     }

     static double xpoint(double x1,double x2)

     {

         double y;

         y=(x1*f(x2)-x2*f(x1))/(f(x2)-f(x1));

         return y;     }

     static double root(double x1,double x2)

     {

         double x,y,y1;

         y1=f(x1);

        do

         {

             x=xpoint(x1,x2);

             y=f(x);

         if(y*y1>0)

         {

            y1=y;

             x1=x;

         }

         else

             x2=x;

     }while(Math.sqrt(y)>=0.00001);

         return x;

         }

}

import java.util.Scanner;

 public class cjava {

     public static void main(String[] args) {

int n;long y;

@SuppressWarnings("resource")

Scanner a=new Scanner(System.in);

System.out.println("please input an integer");

n=a.nextInt();

y=fac(n);

System.out.println(n+"!="+y);

         }

     static long fac(int n) {

         long f;

         if(n<0) {

             System.out.println("n<0,data error!");

             f=-1;

         }

         else if(n==0||n==1)

             f=1;

         else

             f=fac(n-1)*n;

         return f;

     }

     }