/in/foo.c:1:9: error: expected '=', ',', ';', 'asm' or '__attribute__' before '<' token
 include <stdio.h>
         ^
/in/foo.c: In function 'main':
/in/foo.c:5:5: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
     scanf("%lf", &x);
     ^~~~~
/in/foo.c:5:5: warning: incompatible implicit declaration of built-in function 'scanf'
/in/foo.c:5:5: note: include '<stdio.h>' or provide a declaration of 'scanf'
/in/foo.c:15:5: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
     printf("%.3f\n", y);
     ^~~~~~
/in/foo.c:15:5: warning: incompatible implicit declaration of built-in function 'printf'
/in/foo.c:15:5: note: include '<stdio.h>' or provide a declaration of 'printf'