View Compilation Error

0_0_24716843_23293.cpp:8:7: error: 'N' was not declared in this scope
 int a[N];
       ^
0_0_24716843_23293.cpp: In function 'double dfs(int)':
0_0_24716843_23293.cpp:44:22: error: 'a' was not declared in this scope
     ans = max(ans,su(a[i],a[j],a[k]) + dfs(cnt+1));
                      ^
0_0_24716843_23293.cpp: In function 'int main()':
0_0_24716843_23293.cpp:57:16: error: 'a' was not declared in this scope
    scanf("%d",&a[i]);
                ^
0_0_24716843_23293.cpp:59:8: error: 'a' was not declared in this scope
   sort(a,a+n,comp);
        ^