Cailtyn loves fish. In fact, she has 4 tanks in her room filled with a variety of tropical fish. The tanks hold 4200 milliliters, 3600 milliliters, 1500 milliliters and 2000 milliliters. She needs to empty each tank and refill them. She only has a one-liter bottle to use to fill the tanks. How many times will she need to fill the liter bottle to re-fill all of her fish tanks?