You enter a logical virtual tournament. The first problem that is in front of you is as follows:

You have a three liters and a 5 liters measuring jars. There is a huge tank of water behind you comprising of about 100 liters of water. You have to use only these two jars and take out exactly 4 liters of water. How will you do it ?

Let us name the 5 liters and 3 liters jars as A and B respectively.

First fill A completely.

Now fill B with it completely. Now B has 3 liters of water. Pour it out completely. Now fill the remaining 2 liters of water from A to B. Now B has 2 liters of water while A is empty.

Next, Fill A again fully. Now, fill B with it (which had just 1 liters of capacity remaining). Thus now, A has exactly 4 liters of water.