How to extract this information

I have come across questions of this type so many times in C++ that I felt it's about time I learn this technique. I know how it's done in Java, but I'm still a novice in C++.

Suppose I have a text file which contains some dates in this format:

May 3rd, 2014, /
December 4th, 2011, -
January 19th, 200, -
January 1st, 2011, /
March 3rd, 1900, /

The last char in each line is like a date separator as shown below.

How can I convert them to this format and write in another text file:

5/3/2014
12-4-2011
01-19-200
1/1/2011
03/03/1900

The focus here is on string manipulation and not file IO.

My try:

#include <iostream>
#include <fstream>
#include <string>

using namespace std;

int main() {
    ifstream in;
    string s;
    cout << "\nPlease enter the input file name\n";
    cin >> s;
    in.open(s);
    if (in) {
        // Logic goes here
    }
    else {
        cout << "\nCouldn't locate the file.\n";
    }
    cin.get(); 
    return 0;
}