CodeChef ZACKHAN - Zack And The Handkerchieves
algorithm : GCD
In mathematics, the greatest common divisor (gcd) of two or more integers, which are not all zero, is the largest positive integer that divides each of the integers. For example, the gcd of 8 and 12 is 4.[1][2]
The greatest common divisor is also known as the greatest common factor (gcf),[3] highest common factor (hcf),[4] greatest common measure (gcm),[5] or highest common divisor.[6]
source : https://en.wikipedia.org/wiki/Greatest_common_divisor