Instruction: During the certain time you will be shown some numbers. Remember them. Then you should carry out tasks of each level. If you aren't able to complete all actions, enter how many you have remembered.
This exercise conduces to training of short-term memory that improves memorising and retaining much information for executing some mental efforts. When training you improve ability to deal with a wealth of information, at the same time remembering a great number of ongoing results.
This technique conduces to your rarer usage of a pen and paper when making complicated calculations as you will be able to easily retain all intermediate values in your memory.