Play with Arrays

Finally, Chef made a game to play in his free time. The game goes as follows: - Initially, you get an empty array $S$. - You tell the computer an integer $A_{i}$. - If $A_i$ is present in the array, remove it from the array otherwise, add $A_i$ to the array. This operation is repeated $N$ times. At the end of $N$ operations, you need to output the number of integers still present in the array