View Compilation Error

0_0_34975735_19310.cpp:1:7: error: 'maxn' was not declared in this scope
 int a[maxn];
       ^
0_0_34975735_19310.cpp: In function 'int main()':
0_0_34975735_19310.cpp:5:24: error: 'scanf' was not declared in this scope
     while(scanf("%d",&n),n)
                        ^
0_0_34975735_19310.cpp:10:25: error: 'a' was not declared in this scope
             scanf("%d",&a[i]);
                         ^
0_0_34975735_19310.cpp:15:26: error: 'printf' was not declared in this scope
             printf("No\n");
                          ^