while True: try: n = int(input()) temp = [] while len(temp) < n: for i in range(n): x = 2 + 3 * i temp.append(x) a = sum(temp) print(a) except: break
while True: try: n = int(input()) temp = [] while len(temp) < n: for i in range(n): x = 2 + 3 * i temp.append(x) a = sum(temp) print(a) except: break