题解

#include <bits/stdc++.h>
using namespace std;
int main() {
    int n ,add = 2 ,sum = 1;
    cin >> n;
    if (n == 0){
    	cout << 1;
    	return 0;
	}
    for (int i = 1 ; i <= n ; i++){
        sum += add;
        add += 4;
    }
    cout << sum;  //主要是思考过程，题解没什么好看的♂
    return 0;
}