View Compilation Error

0_0_29982652_19976.cpp:4:10: error: 'MAXN' was not declared in this scope
 double a[MAXN];
          ^
0_0_29982652_19976.cpp: In function 'int main()':
0_0_29982652_19976.cpp:8:44: error: 'a' was not declared in this scope
         for(int i=0; i<n; i++)scanf("%lf",&a[i]);
                                            ^
0_0_29982652_19976.cpp:12:59: error: 'a' was not declared in this scope
             for(int j=0; j<n; j++)if((state)&(1<<j))temp+=a[j];
                                                           ^