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Combinatorics Difficulty 8.9 Shortlist Find the answer

Each of the six boxes B1B_1, B2B_2, B3B_3, B4B_4, B5B_5, B6B_6 initially contains one coin. The following operations are allowed

Type 1) Choose a non-empty box BjB_j, 1j51\leq j \leq 5, remove one coin from BjB_j and add two coins to Bj+1B_{j+1};

Type 2) Choose a non-empty box BkB_k, 1k41\leq k \leq 4, remove one coin from BkB_k and swap the contents (maybe empty) of the boxes Bk+1B_{k+1} and Bk+2B_{k+2}.

Determine if there exists a finite sequence of operations of the allowed types, such that the five boxes B1B_1, B2B_2, B3B_3, B4B_4, B5B_5 become empty, while box B6B_6 contains exactly 2010201020102010^{2010^{2010}} coins.

[i]

A number or a short expression. Spacing and $ signs are ignored.

Solution

To solve this problem, we need to analyze the types of operations and their effects on the coin distribution among the six boxes.

Initially, each box B1,B2,B3,B4,B5,B6 B_1, B_2, B_3, B_4, B_5, B_6 contains 1 coin, so the total number of coins in all boxes is 6.

### Analysis of Operations

1. Type 1 Operation:
- Choose a non-empty box Bj B_j (where 1j5 1 \leq j \leq 5 ), remove 1 coin from Bj B_j , and add 2 coins to Bj+1 B_{j+1} .
- Effect: The total number of coins increases by 1 for each Type 1 operation.

2. Type 2 Operation:
- Choose a non-empty box Bk B_k (where 1k4 1 \leq k \leq 4 ), remove 1 coin from Bk B_k , and swap the contents of boxes Bk+1 B_{k+1} and Bk+2 B_{k+2} .
- Effect: The total number of coins remains unchanged as you only remove 1 coin and swap contents.

### Problem Goal

We want boxes B1,B2,B3,B4,B5 B_1, B_2, B_3, B_4, B_5 to become empty while B6 B_6 contains exactly 201020102010 2010^{2010^{2010}} coins. We begin with a total of 6 coins, and ultimately we need exactly 201020102010 2010^{2010^{2010}} coins in box B6 B_6 .

### Coin Count Analysis

Since the Type 1 operation increases the total number of coins, to reach 201020102010 2010^{2010^{2010}} , the number of Type 1 operations needed is:

2010201020106 2010^{2010^{2010}} - 6

### Parity Consideration

Initially, the total number of coins (6) is even. Each Type 1 operation increases the total number of coins by 1, thus switching the parity of the total number of coins from even to odd, and so on.

The target, 201020102010 2010^{2010^{2010}} , is an extremely large exponentiation, but critically, note that 2010201020100(mod2) 2010^{2010^{2010}} \equiv 0 \pmod{2} (since any power of an even number is even).

### Conclusion on Parity

To achieve 201020102010 2010^{2010^{2010}} coins in B6 B_6 , the total number of coins must be even. Starting with an even count (6), any odd number of Type 1 operations results in an odd total, failing to reach the even final amount.

Therefore, it is impossible to use a finite sequence of these operations to reach a scenario where box B6 B_6 contains exactly 201020102010 2010^{2010^{2010}} coins with the others containing none.

Thus, the answer is:

No \boxed{\text{No}}

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Source: Omni-MATH, licensed Apache-2.0. Statement and solution reproduced as published; topic and difficulty added by this site.