View Compilation Error

0_0_21797606_5132.cpp:5:16: error: expected primary-expression before ';' token
 const int maxn=;  
                ^
0_0_21797606_5132.cpp:7:14: error: size of array 'tree' is not an integral constant-expression
 int tree[maxn];
              ^
0_0_21797606_5132.cpp: In function 'int main()':
0_0_21797606_5132.cpp:30:10: error: 'a' was not declared in this scope
   memset(a,0,sizeof(a));  
          ^
0_0_21797606_5132.cpp:38:45: error: 'sum' was not declared in this scope
   for(int i=1;i<=n;++i)   printf("%d ",sum(i));
                                             ^