import Foundation

let (x, n) = readInts().mapToTuple()
let ps = Set(readInts())
print(
    Set(-100...100)
        .symmetricDifference(ps)
        .sorted(by: <)
        .sorted { abs($0 - x) <= abs($1 - x) }
        .first!
)

// MARK: -----------------------------------------------------------------------


func readInt() -> Int {
    Int(readLine()!)!
}

func readInts() -> [Int] {
    readLine()!.split(separator: " ").map { Int($0)! }
}

extension Collection {
    func mapToTuple() -> (Element, Element) {
        var i = makeIterator()
        return (i.next()!, i.next()!)
    }
    func mapToTuple() -> (Element, Element, Element) {
        var i = makeIterator()
        return (i.next()!, i.next()!, i.next()!)
    }
    func mapToTuple() -> (Element, Element, Element, Element) {
        var i = makeIterator()
        return (i.next()!, i.next()!, i.next()!, i.next()!)
    }
}

struct DP<Argument: Hashable, Element> {
    var dictionary = [Argument: Element]()
    
    var expression: (Argument, (Argument) -> Element) -> Element
    
    init(expression: @escaping (_ argument: Argument, _ note: (Argument) -> Element) -> Element) {
        self.expression = expression
    }
    
    subscript(_ argument: Argument) -> Element {
        mutating get {
            if let note = dictionary[argument] {
                return note
            } else {
                let result = expression(argument) { self[$0] }
                dictionary[argument] = result
                return result
            }
        }
    }
}
