Given the Euclidean algorithm steps 105=2⋅42+21105 = 2 \cdot 42 + 21105=2⋅42+21 and 42=2⋅21+042 = 2 \cdot 21 + 042=2⋅21+0, what is the GCD(105,42)\text{GCD}(105, 42)GCD(105,42)?
212121
424242
105105105
777