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## A - Three Integers Editorial by evima

The operation “subtract $$1$$ from two of the integers” can be rephrased into an operation “add $$1$$ to one of the integers and then subtract $$1$$ from all of the integers.” Thus, the problem can be rephrased as follows.

• Find the smallest positive integer $$K$$ for which the following holds.
• It is possible to “add $$1$$ to one of the integers” at most $$K$$ times so that all the integers have the value of $$K$$.

Here, the conditions that $$K$$ must satisfy are the following.

• $$K \geq \max\{A,B,C\}$$, and
• $$K \geq (K-A)+(K-B)+(K-C)$$.

Let $$A \leq B \leq C$$ for simplicity. Then, if the second condition is satisfied for $$K=C$$, the answer is $$C$$; otherwise, it is $$-1$$.

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