package main

import (
    "fmt"
    "math"
)

func main() {
    fmt.Println(get_out_of_order_value([]int64{}))
    fmt.Println(get_out_of_order_value([]int64{6}))
    fmt.Println(get_out_of_order_value([]int64{3, 1, 2, 6, 9}))
    fmt.Println(get_out_of_order_value([]int64{233, 87, 4334, 88, 99424, 123}))
    fmt.Println(get_out_of_order_value([]int64{233, 87, 4, 88, 99424, 123}))
}

func get_out_of_order_value(arr []int64) int64 {
    if len(arr) < 2 { return -1 }

    min := int64(math.MaxInt64)

    for i := range arr {
        if arr[i] < min { min = arr[i] }
    }

    for i, val := range arr {
        nval := val - min

        for {
            if int64(i) == nval || nval > int64(len(arr)) - 1 { break }
            arr[i], arr[nval] = arr[nval], arr[i]
            nval = arr[i] - min
        }
    }

    for i := 0; i < len(arr) - 1; i++ {
        if int64(i) == arr[i] - min { continue }
        return arr[i - 1] + 1
    }

    return -1
}