#include <iostream>
#include <string>
#include <cmath>
#include <algorithm>

int toDecimal(const std::string& num, int base) {
    int decimalValue = 0;
    for (char digit : num) {
        decimalValue *= base;
        decimalValue += (isdigit(digit) ? digit - '0' : digit - 'A' + 10);
    }
    return decimalValue;
}

std::string fromDecimal(int decimalValue, int base) {
    if (decimalValue == 0) return "0";

    std::string result;
    while (decimalValue > 0) {
        int remainder = decimalValue % base;
        result += (remainder < 10 ? '0' + remainder : 'A' + (remainder - 10));
        decimalValue /= base;
    }
    std::reverse(result.begin(), result.end());
    return result;
}

std::string convertBase(const std::string& num, int fromBase, int toBase) {
    return fromDecimal(toDecimal(num, fromBase), toBase);
}

int main() {
    std::string number;
    int fromBase, toBase;

    std::cout << "输入数字：";
    std::cin >> number;
    std::cout << "输入源进制（2-16）：";
    std::cin >> fromBase;
    std::cout << "输入目标进制（2-16）：";
    std::cin >> toBase;

    std::string convertedNumber = convertBase(number, fromBase, toBase);
    std::cout << "转换后的数字是：" << convertedNumber << std::endl;

    return 0;
}