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0_0_39623999_27559.cpp: In function 'int hdu1()':
0_0_39623999_27559.cpp:3:16: error: 'scanf_s' was not declared in this scope
    3 |         while (scanf_s("%d %d", &a, &b) != EOF) {
      |                ^~~~~~~
0_0_39623999_27559.cpp:3:44: error: 'EOF' was not declared in this scope
    3 |         while (scanf_s("%d %d", &a, &b) != EOF) {
      |                                            ^~~
0_0_39623999_27559.cpp:1:1: note: 'EOF' is defined in header '<cstdio>'; did you forget to '#include <cstdio>'?
  +++ |+#include <cstdio>
    1 | int hdu1() {
0_0_39623999_27559.cpp:4:17: error: 'printf' was not declared in this scope
    4 |                 printf("%d\n", a + b);
      |                 ^~~~~~
0_0_39623999_27559.cpp:4:17: note: 'printf' is defined in header '<cstdio>'; did you forget to '#include <cstdio>'?