Main.c: In function ‘main’:
Main.c:6:5: warning: implicit declaration of function ‘scanf_s’; did you mean ‘scanf’? [-Wimplicit-function-declaration]
    6 |     scanf_s("%lf",& a);
      |     ^~~~~~~
      |     scanf
/usr/bin/ld: /tmp/cc5BX7hT.o: in function `main':
Main.c:(.text.startup+0x13): undefined reference to `scanf_s'
collect2: error: ld returned 1 exit status