process.stdin.resume();
process.stdin.setEncoding('ascii');

var input_stdin = "";
var input_stdin_array = "";
var input_currentline = 0;

process.stdin.on('data', function (data) {
    input_stdin += data;
});

process.stdin.on('end', function () {
    input_stdin_array = input_stdin.split("\n");
    main();    
});

function readLine() {
    return input_stdin_array[input_currentline++];
}

/////////////// ignore above this line ////////////////////

const bigNumber = require('bignumber.js');


function sumOfgroup(k) {
    // Return the sum of the elements of the k'th group.
    
    if(k===1)
        return 1;

    var result = new bigNumber(0);
    let first = new bigNumber((k * (k-1)) + 1);
    
    let max = Math.pow(10,6);
    for(let i=0; i<k; i++){
       result = result.plus(first);
       first = first.plus(2); 
    }
    
    return result;
}

function main() {
    var k = parseInt(readLine());
    var answer = sumOfgroup(k);
    process.stdout.write("" + answer + "\n");

}