import java.util.*

fun main(args: Array<String>) {
    val cin = Scanner(System.`in`)
    var N = cin.nextLong()
    var K = cin.nextLong()

    var sm = 0L
    for(i in 1..N) {
        var x = cin.nextInt()
        sm += x
    }

    println(if(sm == K * N) "YES" else "NO")
}