#include<stdio.h>
long int sumOfGroup(int k) {
    long sum=0,start=k;
    start--;
    start = ((start)*(start+1));
    start ++;
    //cout<<"start: "<<start<<endl;
    for(int i=1; i<=k; i++){
        sum+=start;
        start+=2;
    }
    return sum;
}

int main() {
    int k;
    scanf("%i", &k);
    long int answer = sumOfGroup(k);
    printf("%ld\n", answer);
    return 0;
}