C++ Return Factorial with Integers

#include "stdafx.h"
#include<iostream>
#include<string>

using namespace std;

int main()
{
	unsigned int userInput;
	unsigned long long factorial = 1;
	string sum = "0";

	cout << "Enter an integer: ";
	cin >> userInput;

	for (int i = 1; i <= userInput; ++i)
	{
		factorial *= i;
		std::string intCast = std::to_string(i);
		sum = sum + "*" + intCast;
	}

	sum.replace(0, 2, "");//if you don't want to see 0+

	cout << "\nFactorial of " << sum << "=" << factorial;
	cin.get();

	cin.get();

	return 0;
}