Early Beggatings

In the beginning there was Adam:

"And the LORD God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living being." Genesis (2:7)

Then came Eve:

"And the LORD God caused a deep sleep to fall on Adam, and he slept; and He took one of his ribs, and closed up the flesh in its place.

Then the rib which the LORD God had taken from man He made into a woman, and He brought her to the man. (Genesis 2:21-22)

Then the begatting began:

"Now Adam knew Eve his wife, and she conceived and bore Cain, and said, “I have acquired a man from the LORD."

"Then she bore again, this time his brother Abel." (Genesis 4:1-2)

But Cain was a bad boy:

Now Cain talked with Abel his brother; and it came to pass, when they were in the field, that Cain rose up against Abel his brother and killed him. Genesis (4:8)

That, by my count, leaves three people on earth, Adam, Eve and Cain. But, soon comes the third generation of man:

"And Cain knew his wife, and she conceived and bore Enoch." (Genesis 4:17)

Where exactly, it would seem logical to ask, did Cain find a woman to know?

Just curious.