#include <bits/stdc++.h>
#include <cstdint>

using namespace std;

uint64_t sumOfGroup(uint64_t k) {
    // Return the sum of the elements of the k'th group.
    
    // Get first number of sequence
    uint64_t firstN = k*(k+1)/2 - k;
    firstN = firstN*2 + 1;
    //Get last number of the sequence
    uint64_t lastN = k*(k+1)/2 - 1;
    lastN = lastN*2 +1;
    
    //
    uint64_t sol = 0;
    
    for (uint64_t i = firstN; i <= lastN; i+=2)
        sol += i;
        
    return sol;
}

int main() {
    uint64_t k;
    cin >> k;
    uint64_t answer = sumOfGroup(k);
    cout << answer << endl;
    return 0;
}