package main

import (
    "fmt"
    "os"
    "strings"
    "strconv"
    "github.com/thoas/go-funk"
)


func check(e error) {
    if e != nil { panic(e) }
}

func abs(n int) int {
    if n < 0 { return -n }
    return n
}

func pop(arr []int, idx int) []int {
    out := make([]int, len(arr) - 1)

    for i, elem := range arr {
        if i == idx {
            continue
        } else if i > idx {
            out[i - 1] = elem
        } else {
            out[i] = elem
        }
    }

    return out
}

func change(s []int) []int {
    out := make([]int, len(s) - 1)
    for i := range out {
        out[i] = s[i + 1] - s[i]
    }
    return out
}

func validate_change(change []int) bool {
    all_neg      := len( funk.Filter(change, func(x int) bool { return x >= 0     }).([]int) ) == 0
    all_pos      := len( funk.Filter(change, func(x int) bool { return x <= 0     }).([]int) ) == 0
    all_abs_lt_4 := len( funk.Filter(change, func(x int) bool { return abs(x) > 3 }).([]int) ) == 0

    return ( all_neg || all_pos ) && all_abs_lt_4
}

func main() {
    // read in file as lines
    dat, err := os.ReadFile("data.txt")
    check(err)
    
    valid := 0
    lines := strings.Split(string(dat), "\n")
    
    // for every non empty line
    for _, line := range lines {
        if line == "" { continue }
        
        // get numbers as array
        str_levels := strings.Split(line, " ")
        
        // convert to integer
        levels := make([]int, len(str_levels))
        for j := range str_levels {
            levels[j], err = strconv.Atoi(str_levels[j])
            check(err)
        }
        
        // check for valid series
        for i := range levels {
            slice := pop(levels, i)
            if validate_change(change(slice)) {
                valid++
                break
            }
        }
    }

    fmt.Println(valid)
}