#include <bits/stdc++.h>

using namespace std;

long long int arr[1000000] = {0};

void fill_arr(int j)
{
    int y=1, i;
    for(i=0; i<=j; y=y+2,i++)
    {
        //if(i%2 == 1)
        //{
            
            arr[i] = y;
            //j++;
        //cout<<arr[j]<<endl;
            
        //}
        
    }
}

long sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.
    int i=1, idx=0, j, x=0;
    long res = 0;
   
    for(i=1; i<=k; i++)
    {
        idx = idx+i;
    }
    //cout<<"idx="<<idx<<endl;
    //cout<<"val = "<<arr[idx-1]<<endl;
    j=idx-1;
    fill_arr(j);
    for(x=k; x>0; x--)
    {
        res = res+arr[j];
        j--;
    }
    return res;
    
}

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