#include <bits/stdc++.h>

using namespace std;

long int sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.
    long int sum = 0, flag = 0;
    long int x = 1, y = 1;
    for (int i = 1; i < 1000001; i+=2) {
        if (x == k || flag == 1) {
            flag = 1;
            while (x > 0) {
                sum += i;
                //cout << sum << endl;
                x--;
                break;
            }
            if (x == 0) {
              return sum;
            }
            continue;
        }
        if (flag && x == 0) {
            cout << sum << endl;
            return sum;
        }
        while (x > 0) {
            x--;
            break;
        }
        if (x == 0) {
            y++;
            x = y;
        }
    }
    return sum;
}

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