Step 1 :
Divide $ 858 $ by $ 336 $ and get the remainder

$$ 858 : 336 = 2 \text{ ( remainder is } \color{blue}{ 186 } \text{ ) } $$

The remainder is positive ($ 186 > 0 $), so we will continue with division.

Step 2 :
Divide $ 336 $ by $ \color{blue}{ 186 } $ and get the remainder

$$ 336 : 186 = 1 \text{ ( remainder is } \color{blue}{ 150 } \text{ ) } $$

The remainder is still positive ($ 150 > 0 $), so we will continue with division.

Step 3 :
Divide $ 186 $ by $ \color{blue}{ 150 } $ and get the remainder

$$ 186 : 150 = 1 \text{ ( remainder is } \color{blue}{ 36 } \text{ ) } $$

The remainder is still positive ($ 36 > 0 $), so we will continue with division.

Step 4 :
Divide $ 150 $ by $ \color{blue}{ 36 } $ and get the remainder

$$ 150 : 36 = 4 \text{ ( remainder is } \color{blue}{ 6 } \text{ ) } $$

The remainder is still positive ($ 6 > 0 $), so we will continue with division.

Step 5 :
Divide $ 36 $ by $ \color{blue}{ 6 } $ and get the remainder

$$ 36 : \color{blue}{ \boxed { 6 }} = 6 \text{ ( remainder is } \color{blue}{ 0 } \text{ ) } $$

The remainder is zero => GCD is the last divisor $ \color{blue}{ \boxed { 6 }} $.

This solution can be visualized using a Venn diagram.

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

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