View Compilation Error

0_0_36379879_29855.cpp:8:11: error: array bound is not an integer constant before ']' token
 int a[maxn];
           ^
0_0_36379879_29855.cpp: In function 'int main()':
0_0_36379879_29855.cpp:14:24: error: 'a' was not declared in this scope
            scanf("%d",&a[i]);
                        ^
0_0_36379879_29855.cpp:16:16: error: 'a' was not declared in this scope
           sort(a+1,a+1+n);
                ^