题解 | #尼科彻斯定理#

const count = (m) => {
    let first = m * m - m + 1;
    let result = first;
    for(let i = 1; i< m; i++){
        first = first + 2;
        result += '+' + String(first);
    }
    return result;
}
const readline = require('readline');
const rl = readline.createInterface({
    input:process.stdin,
    output:process.stdout
});
rl.on('line',(line)=>{
    console.log(count(line))
})