$\mathbb{\text { Frankin B.P. }}$

In a row, 39 numbers, not equal to zero, are written. The sum of any two adjacent numbers is positive, while the sum of all numbers is negative.

What is the sign of the product of all numbers

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Consider any number with an odd index. The remaining numbers are divided into pairs of adjacent numbers. Thus, their sum is positive, which means the considered number is negative. Numbers with even indices must be positive so that the sums with them in pairs are positive. Therefore, 20 negative numbers and 19 positive numbers are listed, and their product is positive.

## Problem