Recursive function to convert to base

[aidenkael]

#include <iostream>

int Convert(int num, int base)
{
	// What is the formula?
}

int main()
{
	//variables
	int num;
	int base;

	std::cout << "Enter a number: ";
	std::cin >> num;
	std::cout << "Enter a base: ";
	std::cin >> base;

	std::cout << num << " in base " << base << " is :" << Convert(num, base) << std::endl;
	system("pause");
}

I don't need the code, just the formula :)