object Solution {

    def sumOfGroup(k: Int): Long =  {
        //1, 2, 4, 7, 11, 16
        def recur(next: Int): Int = {
            var temp = 0
            if(next == 1){
                temp + 1
            }
            
            else if (next == 2){
                temp = recur(next-1) + 1
                temp
            }
            
            else {
                temp = recur(next-1) + (next-1)
                temp
            }
        }
        val groupLoc = recur(k)
        //println(groupLoc)
        var startLoc = 0
        var result = 1
        startLoc = 1 + (2 * (groupLoc - 1))
        //println(startLoc)
        result = startLoc
        val temp2 = startLoc
        //return startLoc.toLong
        for (i <- 2 to k){
        result = result + temp2 + (2 * (i - 1))
        //temp2 = temp2 + (2 * (i - 1))
            //println(2 * (i - 1))
            //println(temp2)
            //println(result)
            //return result.toLong
        
        }
        return result.toLong
    }

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