#include <iostream>

long sumOfGroup(long k) {
    long sum = 0;
    long k_increment = 0;
    
    sum = (k *(k-1)) + 1;
    k_increment = sum + 2;    
    
    for (long i = 0; i < k - 1; ++i) {
        sum += k_increment;
        k_increment += 2;
    }
    
    return sum;
}

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