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())!
    }
}

var scanner = Scanner()

let N = scanner.nextInt()
var P = [(x: Int, y: Int)]()

for _ in 0 ..< N {
    let x = scanner.nextInt()
    let y = scanner.nextInt()
    P.append((x: x, y: y))
}

var events = [(t: Int, i: Int, j: Int)]()
for i in 0 ..< N {
    for j in i + 1 ..< N {
        let dx = P[j].x - P[i].x
        let dy = P[j].y - P[i].y
        events.append((t: dx * dx + dy * dy, i: i, j: j))
    }
}
events.sort { $0.t < $1.t }

var alive = [Bool](repeating: true, count: N)
var answer = 0
for (_, i, j) in events where alive[i] && alive[j] {
    if i == 0 {
        answer += 1
    } else {
        alive[i] = false
    }
    alive[j] = false
}

print(answer)