<image>

Input

The input contains a single integer a (1 ≤ a ≤ 18257).

Output

Print a single integer output (1 ≤ output ≤ 2·109).

Examples

Input

2


Output

13
"""====================================================================================
   ====================================================================================
   
    ___             _______  ___    _______       ___   ___
   |         /\        |    |   \      |    |  / |   | |   | |\    /|
   |        /  \       |    |    \     |    | /  |   | |   | | \  / |
   |___    /____\      |    |     \    |    |/   |___| |   | |  \/  |
       |  /      \     |    |     /    |    |\   |\    |   | |      |
       | /        \    |    |    /     |    | \  | \   |   | |      |
    ___|/          \___|___ |___/   ___|___ |  \ |  \  |___| |      |
 
       
   ====================================================================================
   ==================================================================================== 
"""
# ♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥

n = int(input())
a = 1
s = 12
for i in range(n-1):
    a += s
    s += 12
print(a)

# ♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥
"""====================================================================================
   ====================================================================================
   
    ___             _______  ___    _______       ___   ___
   |         /\        |    |   \      |    |  / |   | |   | |\    /|
   |        /  \       |    |    \     |    | /  |   | |   | | \  / |
   |___    /____\      |    |     \    |    |/   |___| |   | |  \/  |
       |  /      \     |    |     /    |    |\   |\    |   | |      |
       | /        \    |    |    /     |    | \  | \   |   | |      |
    ___|/          \___|___ |___/   ___|___ |  \ |  \  |___| |      |
 
       
   ====================================================================================
   ==================================================================================== 
"""
