Step 1 : Find prime factorization of each number.

(view steps on how to factor 1 and 56. )

Step 2 : Put a box around factors that are common for all numbers:

Note that in this example numbers do not have any common factors.

Step 3 : Multiply the boxed numbers together:

Since there is no boxed numbers we conclude that $\text{GCD = 1}$.

This solution can be visualized using a Venn diagram.

The GCD equals the product of the numbers at the intersection.