Step 1 :
Divide $ 1078 $ by $ 693 $ and get the remainder

$$ 1078 : 693 = 1 \text{ ( remainder is } \color{blue}{ 385 } \text{ ) } $$

The remainder is positive ($ 385 > 0 $), so we will continue with division.

Step 2 :
Divide $ 693 $ by $ \color{blue}{ 385 } $ and get the remainder

$$ 693 : 385 = 1 \text{ ( remainder is } \color{blue}{ 308 } \text{ ) } $$

The remainder is still positive ($ 308 > 0 $), so we will continue with division.

Step 3 :
Divide $ 385 $ by $ \color{blue}{ 308 } $ and get the remainder

$$ 385 : 308 = 1 \text{ ( remainder is } \color{blue}{ 77 } \text{ ) } $$

The remainder is still positive ($ 77 > 0 $), so we will continue with division.

Step 4 :
Divide $ 308 $ by $ \color{blue}{ 77 } $ and get the remainder

$$ 308 : \color{blue}{ \boxed { 77 }} = 4 \text{ ( remainder is } \color{blue}{ 0 } \text{ ) } $$

The remainder is zero => GCD is the last divisor $ \color{blue}{ \boxed { 77 }} $.

This solution can be visualized using a Venn diagram.

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

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