#include <iostream>
#include <math.h>
#include <vector>
#include <unordered_map>
#include <string>
#include <set>
#include <algorithm>
#include <bitset>
#include <stack>
#include <string>
#define MAX 100010
#define MOD 1000000007
#define vt first
#define idx second

using namespace std;

long sumOfGroup(int k) {
    long long n = k;
    long long m = n*(n-1)/2;
    long long t = m*2 + 1;
    long long result = t;
    for (int i=1;i<k;i++) {
        t += 2;
        result += t;
    }
    return result;
}

int main() {

    int k;
    cin >> k;
    long answer = sumOfGroup(k);
    cout << answer << endl;
    return 0;
}