The numbers from 1 to 20 are written in a row. Players take turns placing plus and minus signs between them. After all the spaces are filled, the result is calculated. If it is even, the first player wins; if it is odd, the second player wins. Who will win

#
The parity of the result does not depend on the placement of the plus and minus signs, but only on the number of odd numbers in the initial set. Since in this case there are 10 (i.e., an even number), the first player wins.

## Answer

First.