View Compilation Error

0_0_38379477_13238.cpp: In function 'int prime(int)':
0_0_38379477_13238.cpp:4:27: error: 'sqrt' was not declared in this scope
  for (i = 2; i <= sqrt(num); i++)
                           ^
0_0_38379477_13238.cpp: In function 'int main()':
0_0_38379477_13238.cpp:14:18: error: 'scanf' was not declared in this scope
  scanf("%d", &num);
                  ^
0_0_38379477_13238.cpp:17:32: error: 'printf' was not declared in this scope
    printf("%d %d\n", i, num - i);
                                ^