`\color{pink}{#Bơ}`

#include <bits/stdc++.h>
#define ll long long
using namespace std;

int main() {
    ll n;
    cin >> n;
    cout << 1 + 3 * (n - 1) * n;
    return 0;
}

`\color{#1AD5F7}{⋆⟡H}\color{#1AD5F7}{a}\color{#4DA6E6}{r}\color{#668EDD}{i}\color{#8077D5}{i}\color{#995FCD}{i}\color{#EA2F90}{⟡⋆}`