function main(input) {
    const number = Number(input.split("\n")[0]);
    const numbers = Array.from({length:number} ,(v, i) => { return(i+1) });
    const result = numbers.reduce((acc, cur) => acc += cur);
    console.log(result);
}

// let input = "3";
// main(input);
main(require("fs").readFileSync("/dev/stdin","utf8"));
  