The Solution

Suppose Jaya had erased the first (316) and the last (355) and written 670. Suppose Ramesh had erased the second (316) and the last but one (354) and written 670. So we would have twenty 670s.

When two of these are erased, 1339 would be written. So we would have ten 1339s.

When two of these are erased, 2677 would be written. So we would have five 2677s. Thus we end up with 13381.

You can always cross-check this with the Smart Scholars Method

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