I need help with a program that I am working on. Basically the program right now takes a decimal number and converts it into whichever base I choose. What I need it to do is accept other inputs initially (binary, hexa, octal) and convert between whichever I choose. Can anyone point me in the right direction? Here is what I have so far:

```
#include <iostream>
#include <stdexcept>
#include <string>
using namespace std;
int main() try
{
cout << "Enter a number and base: ";
int num, base;
if (cin >> num >> base) {
if (base < 2 || base > 36)
throw out_of_range("Invalid base for conversion");
// Define an alphabet for the largest supported base
const string digits("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ");
bool is_neg = num < 0;
string result;
for (; num; num /= base) {
// Note: abs() is done on each digit instead of the whole num
// to preserve the full range of int
result.insert(result.begin(), digits[abs(num % base)]);
}
if (is_neg)
result.insert(result.begin(), '-');
cout << result << '\n';
}
else {
cerr << "Invalid input\n";
}
}
catch (const out_of_range& ex)
{
cerr << ex.what() <<'\n';
}
```