gistfile1.java

import java.io.*;
import java.math.BigInteger;

public class Main {
    public static String inName = "input.txt";
    public static String outName = "output.txt";

    public static void main(String[] args) {
        try {
            String line;
            String result;
            InputStream inputStream = new FileInputStream(inName);
            InputStreamReader fileReader = new InputStreamReader(inputStream);
            BufferedReader bufferedReader = new BufferedReader(fileReader);
            line = bufferedReader.readLine();
            int number = Integer.parseInt(line.split(" ")[0]);
            int power = Integer.parseInt(line.split(" ")[1]);

            BigInteger sum = BigInteger.valueOf(1);
            for (int i = 1; i <= number; i++) {
                int fact = 1;
                for (int j = 1; j <= i; j++) {
                    fact = fact*j;
                }

                BigInteger pow = BigInteger.valueOf(1);
                for (int j = 0; j < power; j++) {
                    pow = pow.multiply(BigInteger.valueOf(fact));
                }

                sum = sum.add(pow);
            }

            result = getLastNonZero(String.valueOf(sum));
            System.out.println(sum);
            System.out.println(result);
            BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(
                    new FileOutputStream(outName)));
            writer.write(result);
            writer.close();
        } catch (java.io.IOException e) {
            e.printStackTrace();
        }
    }

    public static String getLastNonZero(String in) {

        for (int i = in.length() - 1; i >= 0; i--) {
            if (in.charAt(i) != '0') {
                return String.valueOf(in.charAt(i));
            }
        }

        return null;
    }
}