题号：T134705

#include <bits/stdc++.h>


using namespace std;
int main(){
	long long n,arr[55];
	cin>>n;
	arr[0] = 2;
	arr[1] = 3;
	arr[2] = 9;
	arr[3] = 17;
	long long j = 10;
	for(long long i = 4;i <= n;i++){
		arr[i] = arr[i - 1] + j;
		j += 2;
	}
	cout<<arr[n];
	return 0;
}

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