import java.util.Arrays; import java.util.Scanner; public class Main { public static void main(String[] args) { Scanner sc = new Scanner(System.in); int ducks = sc.nextInt(); int[] x = new int[ducks]; for (int i = 0; i < ducks; i++) { x[i] = sc.nextInt(); } Arrays.sort(x); int diff = x[1] - x[0]; if (diff == 0) { System.out.println("NO"); return; } for (int i = 1; i < ducks - 1; i++) { if (x[i] - x[i + 1] != diff) { System.out.println("NO"); return; } } System.out.println("YES"); } }