n=int(input())
a=[0 for i in range(n+1)]
for i in range(1,n+1):
    if(i==1):
        a[1]=2
    else:
        a[i]=a[i-1]+2*(i-1)
print(a[n])
/**************************************************************
	Problem: 1366
	User: admin
	Language: Python
	Result: Accepted
	Time:182 ms
	Memory:34868 kb
****************************************************************/