How to Format a Time String with C# in Unity 3D

/// <summary>
/// Formats the input string (in seconds) as a human readable 
/// string in the form of MM:SS.
/// </summary>
/// <returns>
/// A <see cref="System.String"/> of the current playing time.
/// </returns>
private string formatedTimeString (string input) {
    int seconds;
    int minutes;
 
    minutes = Mathf.FloorToInt(input / 60);
    seconds = Mathf.FloorToInt(input - minutes * 60);
    string r = (minutes < 10) ? "0" + minutes.ToString() : minutes.ToString();
    r += ":";
    r += (seconds < 10) ? "0" + seconds.ToString() : seconds.ToString();
    return r;
}