import Foundation

struct Coord : Hashable, CustomStringConvertible {
    let x: Int
    let y: Int
    var description: String { return "(\(x), \(y))" }
    func neighbors() -> [Coord] {
        return [
            Coord(x: x-1, y: y), Coord(x: x+1, y: y),
            Coord(x: x, y: y-1), Coord(x: x, y: y+1)
        ]
    }
    func valid(xLimit: Int, yLimit: Int) -> Bool {
        return x >= 0 && y >= 0 && x < xLimit && y < yLimit
    }
}

func readInput(_ filePath: String) throws -> ([Int:Set<Coord>], Int, Int) {
    let content = try String(contentsOfFile: filePath, encoding: .ascii)
    let lines = content.split(separator: "\n").map(Array.init)
    let map = lines.map { $0.map(String.init).map { Int($0)! } }
    var topo: [Int:Set<Coord>] = [:]
    map.enumerated().forEach { i, row in
        row.enumerated().forEach { j, h in
            topo[h] = (topo[h] ?? []).union([Coord(x: i, y: j)])
        }
    }
    return (topo, lines.count, lines[0].count)
}

let (topo, height, width) = try readInput(CommandLine.arguments[1])
var answer: Int = 0
//topo.forEach { k, v in print("\(k): \(v)") }

for start in topo[0]! {
    var froms: Set<Coord> = [start]
    for altitude in 1...9 {
        var tos: Set<Coord> = []
        for from in froms {
            from.neighbors()
                .filter { c in c.valid(xLimit: height, yLimit: width) }
                .filter { c in topo[altitude]!.contains(c) }
                .forEach { c in tos.insert(c) }
        }
        froms = tos
    }
    answer += froms.count
}
print(answer)