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 ////////////////////

function sumOfgroup(k) {

    
    let sum = 0;
    let oddArr = [];
    let limit = Math.pow(10,6);
    
    // populate array with odd numbers
    for (let i = 0; i < limit; i++) {
        if (i % 2 != 0) oddArr.push(i);
     }
    
   // find index of group K
   let num = k - 1;
   let kIndex = num * (num + 1) / 2
   
   // get sum of odd numbers in group K
   for(let i = kIndex; i < (kIndex + k); i++) {
        sum += oddArr[i]; 
    }
    
    return sum;
    
}

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

}