题解 | #序列找数# 攒人品

// const readline=require("readline")
// const rl=readline.createInterface({
//     input:process.stdin,
//     output:process.stdout
// })
// const arr=[]
// let max
// rl.on("line",function(line){
//     arr.push(parseInt(line))
//     max=arr[0]
// })
const readline = require("readline");
const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
});
let arr
let max
rl.on("line", function(line) {
    arr=line.split(" ")
    arr=arr.map((item)=>parseInt(item))
    max=arr[0]
        });
rl.on("close",function(){
    const sum=(max/2)*(max+1)
    arr.shift()
    const sum1=arr.reduce((a,b)=>a+b)
    console.log(sum-sum1)
})