View Compilation Error

0_0_36448042_14486.cpp:8:24: error: 'mod' was not declared in this scope
 ll power(ll x, int y = mod - 2) {
                        ^
0_0_36448042_14486.cpp: In function 'long long int power(long long int, int)':
0_0_36448042_14486.cpp:11:29: error: 'mod' was not declared in this scope
   if(y & 1) ans = x * ans % mod;
                             ^
0_0_36448042_14486.cpp:13:15: error: 'mod' was not declared in this scope
   x = x * x % mod;
               ^
0_0_36448042_14486.cpp: In function 'int main()':
0_0_36448042_14486.cpp:19:38: error: 'mod' was not declared in this scope
   cout << (n + 1) * power(2ll * n) % mod << endl;
                                      ^