HDU 1042 N! 大數 階乘

import java.math.BigInteger;
import java.util.Scanner;

public class Main{
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while(scanner.hasNext()){
            int n = scanner.nextInt();
            BigInteger ans = new BigInteger("1");
            for (int i = 1; i <= n; i++) ans = ans.multiply(new BigInteger("" + i));
            System.out.println(ans);
        }
    }
}