질문있습니다

아무리 영상을 다시 재생하면서 봐도 똑같이 적었는데 실행시키면 문제 번호가 짝수만 나오게 됩니다 왜 그러는걸까요

#include <stdio.h>
#include <time.h>

int arrayAnimal[4][5];
int checkAnimal[4][5];
char * strAnimal[10];

void initAnimalArray();
void initAnimalName();
void shuffleAnimal();
int getEmptyPosition();
int conv_pos_x(int x);
int conv_pos_y(int y);
void printAnimals();
void printQuestion();

int main(void)
{
	srand(time(NULL));

	initAnimalArray();
	initAnimalName();

	shuffleAnimal();

	int failCount = 0;

	while (1)
	{
		int select1 = 0;
		int select2 = 0;

		printAnimals();
		printQuestion();
		printf("뒤집을 카드를 2개 고르세요 : ");
		scanf_s("%d %d", &select1, &select2);

		if (select1 == select2)
			continue;

		int firstSelect_x = conv_pos_x(select1);
		int firstSelect_y = conv_pos_x(select1);

		int secondSelect_x = conv_pos_x(select2);
		int secondSelect_y = conv_pos_x(select2);

		if ((checkAnimal[firstSelect_x][firstSelect_y] == 0
			&& checkAnimal[secondSelect_x][secondSelect_y] == 0)

			&&

			(arrayAnimal[firstSelect_x][firstSelect_y]
				== arrayAnimal[secondSelect_x][secondSelect_y])
			)
		{
			printf("\n\n 빙고! : %s 발견\n\n", strAnimal[arrayAnimal[firstSelect_x][firstSelect_y]]);
			checkAnimal[firstSelect_x][firstSelect_y] = 1;
			checkAnimal[secondSelect_x][secondSelect_y] = 1;
		}
		else
		{
			printf("\n\n 땡!! (틀렸거나, 이미 뒤집힌 카드입니다)\n");
			printf("%d : %s\n", select1, strAnimal[arrayAnimal[firstSelect_x][firstSelect_y]]);
			printf("%d : %s\n", select2, strAnimal[arrayAnimal[secondSelect_x][secondSelect_y]]);
			printf("\n\n");

			failCount++;
		}

		if (foundAllAnimals() == 1)
		{
			printf("\n\n 축하합니다 ! 모든 동물을 다 찾았네요 \n");
			printf("지금까지 총 %d 번 실수하였습니다\n", failCount);
			break;
		}
	}

	return 0;
}

void initAnimalArray()
{
	for (int i = 0; i < 4; i++)
	{
		for (int j = 0; j < 5; j++)
		{
			arrayAnimal[i][j] = -1;
		}
	}
}

void initAnimalName()
{
	strAnimal[0] = "원숭이";
	strAnimal[1] = "하마";
	strAnimal[2] = "강아지";
	strAnimal[3] = "고양이";
	strAnimal[4] = "돼지";
	strAnimal[5] = "코끼리";
	strAnimal[6] = "기린";
	strAnimal[7] = "낙타";
	strAnimal[8] = "타조";
	strAnimal[9] = "호랑이";
}

void shuffleAnimal()
{
	for (int i = 0; i < 10; i++)
	{
		for (int j = 0; j < 2; j++)
		{
			int pos = getEmptyPosition();
			int x = conv_pos_x(pos);
			int y = conv_pos_y(pos);

			arrayAnimal[x][y] = i;
		}

	}
}

int getEmptyPosition()
{
	while (1)
	{
		int randPos = rand() % 20;
		int x = conv_pos_x(randPos);
		int y = conv_pos_y(randPos);

		if (arrayAnimal[x][y] == -1)
		{
			return randPos;
		}
	}
	return 0;
}

int conv_pos_x(int x)
{
	return x / 5;
}

int conv_pos_y(int y)
{
	return y % 5;
}

void printAnimals()
{
	printf("\n=====이건 비밀인데.. 몰래 보여줍니다=====\n\n");
	for (int i = 0; i < 4; i++)
	{
		for (int j = 0; j < 5; j++)
		{
			printf("%8s", strAnimal[arrayAnimal[i][j]]);
		}
		printf("\n");
	}
	printf("\n===================================\n\n");
}
void printQuestion()
{
	printf("\n\n(문제)\n");
	int seq = 0;

	for (int i = 0; i < 4; i++)
	{
		for (int j = 0; j < 5; j++)
		{
			if (checkAnimal[i][j] != 0)
			{
				printf("%8s", strAnimal[arrayAnimal[i][j]]);
			}
			else
			{
				printf("%8d", seq++);
			}
			seq++;
		}
		printf("\n");
	}
}

int foundAllAnimals()
{
	for (int i = 0; i < 4; i++)
	{
		for (int j = 0; j < 5; j++)
		{
			if (checkAnimal[i][j] == 0)
			{
				return 0;
			}
		}
	}
	return 1;
}

int firstSelect_x = conv_pos_x(select1);
int firstSelect_y = conv_pos_x(select1); // conv_pos_y 로 바뀌어야 합니다

int secondSelect_x = conv_pos_x(select2);
int secondSelect_y = conv_pos_x(select2); // conv_pos_y 로 바뀌어야 합니다