struct Scanner {
    private var elements = [String]()
    private var index = 0

    mutating func peek() -> String {
        while elements.count == index {
            elements = readLine()!.split(separator: " ").map(String.init)
            index = 0
        }
        return elements[index]
    }

    mutating func next() -> String {
        let value = peek()
        index += 1
        return value
    }

    mutating func nextInt() -> Int {
        return Int(next())!
    }

    mutating func nextDouble() -> Double {
        return Double(next())!
    }
}

struct UnionFind {
    var parent: [Int]
    var count: [Int]

    init(_ n: Int) {
        parent = Array(0 ..< n)
        count = [Int](repeating: 1, count: n)
    }

    mutating func find(_ v: Int) -> Int {
        if v == parent[v] {
            return v
        }
        parent[v] = find(parent[v])
        return parent[v]
    }

    mutating func union(_ u: Int, _ v: Int) {
        var u = find(u)
        var v = find(v)
        guard u != v else { return }
        if count[u] < count[v] {
            swap(&u, &v)
        }
        count[u] += count[v]
        parent[v] = u
    }

    mutating func count(_ u: Int) -> Int {
        count[find(u)]
    }
}

struct Array2D<Element> {
    let n1: Int
    let n2: Int
    private var elements: [Element]

    init(repeating: Element, _ n1: Int, _ n2: Int) {
        self.n1 = n1
        self.n2 = n2
        self.elements = [Element](repeating: repeating, count: n1 * n2)
    }

    subscript(i: Int, j: Int) -> Element {
        get {
            elements[i * n2 + j]
        }
        set {
            elements[i * n2 + j] = newValue
        }
    }
}

var scanner = Scanner()
let N = scanner.nextInt()
let A = (0 ..< N).map { _ in scanner.nextInt() }.sorted()
var even = [Int: Int]()

var answer = N
for i in (0 ..< N).reversed() {
    answer += even[A[i] + 1] ?? 0
    even[A[i]] = (even[A[i] + 2] ?? 0) + 1
}

//if even.keys.contains(1) && even.keys.contains(2) {
//    var i = 4
//    while even.keys.contains(i) {
//        print(even[i], i)
//        answer += even[i] ?? 0
//        i += 2
//    }
//}

print(answer)