/in/foo.c: In function 'main':
/in/foo.c:6:2: warning: implicit declaration of function 'gets' [-Wimplicit-function-declaration]
  gets(b); gets(a); 
  ^~~~
/in/foo.c:15:2: warning: implicit declaration of function 'puts' [-Wimplicit-function-declaration]
  puts(a);
  ^~~~
/tmp/ccQFBNLj.o: In function `main':
foo.c:(.text.startup+0x16): warning: the `gets' function is dangerous and should not be used.