View Compilation Error

0_0_27659033_10801.cpp: In function 'int main()':
0_0_27659033_10801.cpp:13:24: error: 'scanf' was not declared in this scope
  while (scanf("%s", str) != EOF)
                        ^
0_0_27659033_10801.cpp:13:29: error: 'EOF' was not declared in this scope
  while (scanf("%s", str) != EOF)
                             ^
0_0_27659033_10801.cpp:27:33: error: 'sscanf' was not declared in this scope
    sscanf(zhan[i], "%d", &num[i]);
                                 ^
0_0_27659033_10801.cpp:30:24: error: 'printf' was not declared in this scope
    printf("%d ", num[i]);
                        ^
0_0_27659033_10801.cpp:31:28: error: 'printf' was not declared in this scope
   printf("%d\n", num[k - 1]);
                            ^