import Foundation

func readInput(filePath: String) -> [[Int?]]? {
    let content =  try? String(contentsOfFile: filePath, encoding: .ascii)
    let lines = content?.split(separator: "\n")
    return lines?.map { $0.split(separator: " ").map { Int($0) } }
}

func safe(_ report: [Int?]) -> Bool {
    if report.contains(nil) {
        return false
    }
    let diffs = zip(report.dropFirst(), report).map { $0.0! - $0.1! }
    return diffs.allSatisfy { abs($0) >= 1 }
        && diffs.allSatisfy { abs($0) <= 3 }
        && (diffs.allSatisfy { $0 > 0 } || diffs.allSatisfy { 0 > $0 })
}

func drop<T>(_ l: [T], at: Int) -> [T] {
    return l.enumerated().filter { $0.0 != at }.map { $0.1 }
}

func mutate<T>(_ l: [T]) -> [[T]] {
    return (0..<l.count).map { drop(l, at: $0) }
}

let reports = readInput(filePath: CommandLine.arguments[1])
let answer = reports!.map(mutate).filter { $0.contains(where: safe) }.count
print(answer)