import java.util.*

fun main(args:Array<String>){
    solve()
}

fun solve(){
    val a = readLine()!!.split(" ").map{it.toInt()}.sorted()
    var ok = true
    for(i in 0 until 3){
        if(a[i] + 1 != a[i + 1]) ok = false
    }
    println(if(ok) "Yes" else "No")
}