N! java

 import java.util.*;
 import java.math.*;

 public class Num2{
     public static void main(String args[]){
         BigInteger s;
         int n;
         Scanner cin = new Scanner(System.in);
         while(cin.hasNext()){
             n = cin.nextInt();
             s = BigInteger.ONE;
             for(int i = ; i <= n; i++){
                 s = s.multiply(BigInteger.valueOf(i));
             }
             System.out.println(s);
         }
     }
 }