Finding the distance from the enemy to the player, would this work?

Im trying to use the distance formula to find the distance between the player and the enemy, does anyone know why this might not work I keep getting errors:

error: CS0236: A field initializer cannot reference the nonstatic field, method, or property `ZombieLogic.Y’ (And same thing happens with X)

public GameObject enemy;
	public GameObject player;


	float y2 = player.transform.position.y;
	float y1 = enemy.transform.position.y;

	float x2 = player.transform.position.x;
	float x1 = enemy.transform.position.y;

	float newY = y2 - y1;
	float newX = x2 - x1;

	float Y = newY * newY;
	float X = newX * newX;

	float Answer = Y + X;

	float Distance = Mathf.Pow (Answer,Answer);

You can just use var distance = Vector3.Distance(objectOne, objectTwo);