int lineFull;
int morePicture;
int lineLong = 3;
int massPicture = 52;
lineFull = massPicture / lineLong;
morePicture = massPicture % lineLong;
Console.WriteLine("Полных рядов - " + lineFull);
Console.WriteLine("Осталось " + morePicture + " картинок");