题解 | 牛牛学数列4

const rl = require("readline").createInterface({ input: process.stdin });

function qhgs(n){
    return n*(n+1)/2;
}

rl.on("line", (input) => {
    let result = 0;
    num = input*1;
    for(let i = 1;i<=input;i++){
        result += qhgs(i)
    }


    console.log(result);
    rl.close();
});