import std.console.*

var lastChr = Option<Rune>.None

func untilDouble9(newChr: Rune): Bool {
    //如果上一个字符存在
    if (let Some(last) <- lastChr) {
        //如果上一个字符和现在的字符都是9
        if (last == r'9' && newChr == r'9') {
            return true
        } else {
            lastChr = newChr
            return false
        }
    } else {
        lastChr = newChr
    }

    return false
}

main() {
    println("Input string, including two consecutive Runeacters 9:")
    try {
        //读取字符串,如果读取的内容包括两个连续的9，就返回截止到这两个9的子字符串
        var input = Console.stdIn.readUntil(untilDouble9)

        //判断结果是不是None，是就继续循环
        while (let None <- input) {
            //重新读取
            input = Console.stdIn.readUntil(untilDouble9)
        }

        println(input.getOrThrow())
    } catch (e: Exception) {
        println("An error occurred:" + e.message)
    }
}