import java.util.Scanner;

public class uml10_10 {

    // 将任意进制字符串转换为十进制整数  
    public static int toDecimal(String number, int base) {
        int decimal = 0;
        int power = 0;
        //还好还好
        // 从字符串的末尾开始处理  
        for (int i = number.length() - 1; i >= 0; i--) {
            char digit = number.charAt(i);

            // 如果是数字字符（0-9）  
            if (Character.isDigit(digit)) {
                int value = Character.getNumericValue(digit);
                decimal += value * Math.pow(base, power);
            }
            // 如果是字母字符（A-F 或 a-f），表示10-15  
            else if (Character.isLetter(digit)) {
                char upperDigit = Character.toUpperCase(digit);
                int value = upperDigit - 'A' + 10;
                decimal += value * Math.pow(base, power);
            } else {
                throw new IllegalArgumentException("Invalid character in number: " + digit);
            }

            power++;
        }

        return decimal;
    }

    // 将十进制整数转换为任意进制字符串  
    public static String fromDecimal(int number, int base) {
        if (number == 0) {
            return "0";
        }

        StringBuilder result = new StringBuilder();
        char[] digits = "0123456789ABCDEF".toCharArray(); // 支持到16进制  

        boolean isNegative = number < 0;
        if (isNegative) {
            number = -number;
        }

        while (number > 0) {
            int remainder = number % base;
            result.insert(0, digits[remainder]);
            number /= base;
        }

        if (isNegative) {
            result.insert(0, '-');
        }

        return result.toString();
    }

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

        System.out.print("请输入源进制（2-16）：");
        int sourceBase = scanner.nextInt();
        scanner.nextLine(); // 消耗掉换行符

        System.out.print("请输入目标进制（2-16）：");
        int targetBase = scanner.nextInt();
        scanner.nextLine(); // 消耗掉换行符

        System.out.print("请输入要转换的" + sourceBase + "进制数字：");
        String number = scanner.nextLine().trim(); // 读取实际的数字输入

        // 验证源进制数字是否有效
        for (char c : number.toCharArray()) {
            if (!Character.isDigit(c) && !(Character.isLetter(c) && (Character.toUpperCase(c) >= 'A' && Character.toUpperCase(c) <= 'F') && sourceBase > 10)) {
                throw new IllegalArgumentException("Invalid character in source base number: " + c);
            }
        }

        // 将源进制数字转换为十进制
        int decimalNumber = toDecimal(number, sourceBase);

        // 将十进制数字转换为目标进制
        String convertedNumber = fromDecimal(decimalNumber, targetBase);

        System.out.println("转换后的" + targetBase + "进制数字是：" + convertedNumber);

        scanner.close();
    }
}