/in/foo.c: In function 'main':
/in/foo.c:4:2: warning: implicit declaration of function 'gets' [-Wimplicit-function-declaration]
  gets(s);
  ^~~~
/in/foo.c:6:2: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
  scanf("%d",&k);  
  ^~~~~
/in/foo.c:6:2: warning: incompatible implicit declaration of built-in function 'scanf'
/in/foo.c:6:2: note: include '<stdio.h>' or provide a declaration of 'scanf'
/in/foo.c:15:2: warning: implicit declaration of function 'puts' [-Wimplicit-function-declaration]
  puts(s);
  ^~~~
/tmp/ccRhDWt7.o: In function `main':
foo.c:(.text.startup+0xf): warning: the `gets' function is dangerous and should not be used.