foo.c: In function 'main':
foo.c:6:12: warning: implicit declaration of function 'scanf_s'; did you mean 'scanf'? [-Wimplicit-function-declaration]
    6 |     while (scanf_s("%lld%lld", &x1, &x2)
      |            ^~~~~~~
      |            scanf
foo.c:6:41: error: expected ')' before '{' token
    6 |     while (scanf_s("%lld%lld", &x1, &x2)
      |           ~                             ^
      |                                         )
    7 |     {
      |     ~                                    
foo.c:13:5: error: expected expression before '}' token
   13 |     }
      |     ^

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