In a pile of 4 coins, only one coin is counterfeit and rest 3 are genuine. All genuine coins weigh exactly the same, whereas the counterfeit coin is heavier or lighter than the others. It is not known, whether the counterfeit coin is heavier or lighter than other genuine coins. What is known is that it is different than genuine. A weighing balance machine is available, which can identify which side is heavier, without giving the exact quantified weights.
How will you identify the counterfeit coin in only 2 weighings?