To find the greatest common divisor of 77 and 187 using the Euclidean algorithm involves the process of long division, which you might have first encountered in elementary school. Divide 77 into 187.

Thomas Koshy, 80.48 The Euclidean Algorithm via Matrices and a Calculator, The Mathematical Gazette, Vol. 80, No. 489 (Nov., 1996), pp. 570-574 ...