Feeling a little rusty upstairs after a relaxing weekend? Nothing gets those gears turning smoothly again like a little mental exercise, so loosen up those lobes and take a look at the problem below!

8809=6　　5555=0
7111=0 　 8193=3
2172=0　　8096=5
6666=4　　1012=1
1111=0　　7777=0
3213=0　　9999=4
7662=2　　7756=1
9313=1　　6855=3
0000=4　　9881=5
2222=0　　5531=0
3333=0　　2581=???

Find the value of ???

The problem was posted to Google + by engineer Eric Martindale, accompanied by the following explanation:

“This problem can be solved by pre-school children in five to ten minutes, by programmers in an hour and by people with higher education… well, check for yourself!”

We had everyone at our office in Tokyo take a crack at it, with one of our reporters producing the answer in about a minute and another two taking a good twenty minutes.

The original writer of this article, however, mulled over it for about an hour before giving up and having someone else explain the answer to him, claiming that his brain is far too developed for this kind of childish poppycock.

The solution is posted at the bottom of this page, so start your timers and let us know how long it took you in the comments below!

PS: We remembered another one that supposedly comes easier to children than to adults:

Complete the sequence: O T T F F…

Source: Google+/Eric Martindale

【SOLUTION BELOW】
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???? = the total number of circles in the four digits. Therefore, 2581 = 2
[ Read in Japanese ]