import java.math.BigInteger

fun main(args: Array<String>) {
    val n = readLine()!!.toInt()
    val v = readLine()!!.split(" ").map(String::toInt)
    val sum = v.sum()
    if(sum % 2 != 0){
        println("impossible");
        return
    }
    var ans = BigInteger.ONE
    for (i in v){
        ans = ans.or(ans.shiftLeft(i))
    }
    if(ans.testBit(sum/2)){
        println("possible")
    }else {
        println("impossible")
    }
}