View Compilation Error

0_0_18996724_10761.cpp: In function 'int main()':
0_0_18996724_10761.cpp:5:21: error: 'scanf' was not declared in this scope
  while (scanf("%s",a)!=EOF&&a[0])
                     ^
0_0_18996724_10761.cpp:5:24: error: 'EOF' was not declared in this scope
  while (scanf("%s",a)!=EOF&&a[0])
                        ^
0_0_18996724_10761.cpp:14:26: error: 'printf' was not declared in this scope
   if (!ans)  printf("9\n");
                          ^
0_0_18996724_10761.cpp:15:26: error: 'printf' was not declared in this scope
   else printf("%d\n", ans);
                          ^