View Compilation Error

0_0_24885094_22817.cpp: In function 'int main()':
0_0_24885094_22817.cpp:9:24: error: 'maxn' was not declared in this scope
     for(int i = 1; i < maxn; ++i){
                        ^
0_0_24885094_22817.cpp:10:27: error: 'mod' was not declared in this scope
         N[i]=N[i-1]*(ll)i%mod;
                           ^
0_0_24885094_22817.cpp:19:28: error: 'S2' was not declared in this scope
             ans=(ans+(N[i]*S2[n][i]%mod))%mod;
                            ^
0_0_24885094_22817.cpp:19:37: error: 'mod' was not declared in this scope
             ans=(ans+(N[i]*S2[n][i]%mod))%mod;
                                     ^