How to make partially overlapping curves into whole curve

HI. I am working on the contour line now.
In the process of combining layers 1 and 2, a segment that overlaps with each other does not become a single complete curve.
How to get rid of overlapping parts and make one whole curve.
Please tell me how to convert these two curves into one without using kangaroos.
question.3dm (3.0 MB) (26.3 KB)