Step 1 :
Divide $ 2040 $ by $ 629 $ and get the remainder

$$ 2040 : 629 = 3 \text{ ( remainder is } \color{blue}{ 153 } \text{ ) } $$

The remainder is positive ($ 153 > 0 $), so we will continue with division.

Step 2 :
Divide $ 629 $ by $ \color{blue}{ 153 } $ and get the remainder

$$ 629 : 153 = 4 \text{ ( remainder is } \color{blue}{ 17 } \text{ ) } $$

The remainder is still positive ($ 17 > 0 $), so we will continue with division.

Step 3 :
Divide $ 153 $ by $ \color{blue}{ 17 } $ and get the remainder

$$ 153 : \color{blue}{ \boxed { 17 }} = 9 \text{ ( remainder is } \color{blue}{ 0 } \text{ ) } $$

The remainder is zero => GCD is the last divisor $ \color{blue}{ \boxed { 17 }} $.

This solution can be visualized using a Venn diagram.

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

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