object Solution {

    def groupIndex(k: Long): Long = {
        def iter(x: Long, prevAcc: Long, acc: Long): Long = 
            if (x == 1) prevAcc
            else if (x == 2) acc
            else iter(x-1, acc, acc+x-1)
        iter(k, 1, 2)
    }
    
    def oddList(k: Long): List[Long] = {
        val i = groupIndex(k)
        val first: Long = i*2-1
        val big1: Long = 1
        (big1 to k).map(x => first + (x-1)*2).toList
    }
    
    def sumOfGroup(k: Long): Long = 
        oddList(k).sum

    def main(args: Array[String]) {
        val sc = new java.util.Scanner (System.in);
        var k = sc.nextInt();
        val answer = sumOfGroup(k);
        println(answer)
    }
}