View Compilation Error

0_0_27427482_29336.cpp: In function 'int main()':
0_0_27427482_29336.cpp:13:24: error: 'scanf' was not declared in this scope
    while(~scanf("%d",&a))
                        ^
0_0_27427482_29336.cpp:14:22: error: 'printf' was not declared in this scope
 printf("%lld\n",hn(a));}
                      ^