A thief steals 4 gallons of liquid soap kept in a train compartment's bathroom from a container that is full of liquid soap. He then fills it with water to avoid detection. Unable to resist the temptation he steals 4 gallons of the mixture again, and fills it with water. When a liquid soap is checked at a station it is found that the ratio of the liquid soap now left in the container to that of water in it is 36:13. What was the initial amount of the liquid soap in the container.