#include<iostream>                                                              
using namespace std;                                                            
                                                                                
int main() {                                                                    
    long k;                                                                     
    cin >> k;                                                                   
    long long start = k*(k-1)/2;                                                
    long long startv = start * 2 + 1;                                           
    long long c = 0;                                                            
    for (long i=0; i<k; i++) {                                                  
        c += startv;                                                            
        startv += 2;                                                            
    }                                                                           
    cout << c;                                                                  
    return 0;                                                                   
}