View Compilation Error

0_0_21221549_16059.cpp: In function 'int main()':
0_0_21221549_16059.cpp:19:16: error: 'a' was not declared in this scope
         memset(a,0,sizeof(Node)*MAXN);  
                ^
0_0_21221549_16059.cpp:19:27: error: 'Node' was not declared in this scope
         memset(a,0,sizeof(Node)*MAXN);  
                           ^