import java.util.*

fun main(args: Array<String>) {
    val cin = Scanner(System.`in`)
    var N = cin.nextInt()
    var K = cin.nextLong()
    val asc = Array(N, { i -> cin.nextLong() })

    var sm = 0L
    for(i in 1..N) sm += asc[i - 1]

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