import java.util.Scanner;

public class BaseConversion {

    // 将任意R进制数转换为十进制数
    public static int convertToDecimal(String numStr, int base) {
        return Integer.parseInt(numStr, base);
    }

    // 将十进制数转换为任意R进制数
    public static String convertFromDecimal(int num, int base) {
        if (num == 0) {
            return "0";
        }
        StringBuilder result = new StringBuilder();
        while (num > 0) {
            int remainder = num % base;
            if (remainder < 10) {
                result.append(remainder);
            } else {
                result.append((char) ('A' + (remainder - 10))); // A-F 对应 10-15
            }
            num /= base;
        }
        return result.reverse().toString(); // 反转结果
    }

    // 将一个R进制数转换为另一个R进制数
    public static String convertBase(String numStr, int fromBase, int toBase) {
        int decimalNumber = convertToDecimal(numStr, fromBase);
        return convertFromDecimal(decimalNumber, toBase);
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.print("请输入要转换的数字: ");
        String numStr = scanner.nextLine();

        System.out.print("请输入源进制 (2-16): ");
        int fromBase = scanner.nextInt();

        System.out.print("请输入目标进制 (2-16): ");
        int toBase = scanner.nextInt();

        // 验证进制范围
        if (fromBase < 2 || fromBase > 16 || toBase < 2 || toBase > 16) {
            System.out.println("进制必须在 2 到 16 之间。");
        } else {
            String result = convertBase(numStr, fromBase, toBase);
            System.out.println(numStr + " 从 " + fromBase + " 进制转换到 " + toBase + " 进制的结果是: " + result);
        }

        scanner.close();

        //This is a test
    }
}