Step 1 :
Divide $ 2020 $ by $ 456 $ and get the remainder

$$ 2020 : 456 = 4 \text{ ( remainder is } \color{blue}{ 196 } \text{ ) } $$

The remainder is positive ($ 196 > 0 $), so we will continue with division.

Step 2 :
Divide $ 456 $ by $ \color{blue}{ 196 } $ and get the remainder

$$ 456 : 196 = 2 \text{ ( remainder is } \color{blue}{ 64 } \text{ ) } $$

The remainder is still positive ($ 64 > 0 $), so we will continue with division.

Step 3 :
Divide $ 196 $ by $ \color{blue}{ 64 } $ and get the remainder

$$ 196 : 64 = 3 \text{ ( remainder is } \color{blue}{ 4 } \text{ ) } $$

The remainder is still positive ($ 4 > 0 $), so we will continue with division.

Step 4 :
Divide $ 64 $ by $ \color{blue}{ 4 } $ and get the remainder

$$ 64 : \color{blue}{ \boxed { 4 }} = 16 \text{ ( remainder is } \color{blue}{ 0 } \text{ ) } $$

The remainder is zero => GCD is the last divisor $ \color{blue}{ \boxed { 4 }} $.

This solution can be visualized using a Venn diagram.

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

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