#include <bits/stdc++.h>
#define LL long long int
#define MAX 1000005
using namespace std;


int main() {
    LL i, j, n, k;
    LL p[MAX] = {0};
    LL curr = 0;
    for(i=1;i<MAX;i++) {
        p[i] = curr;
        curr += i;
    }
    cin>>k;
    LL st = 2 * p[k] + 1;
    LL ans = 0;
    for(i=0;i<k;i++) {
        ans += st;
        st+=2;
    }
    cout<<ans<<endl;
    return 0;
}