/in/foo.c: In function 'main':
/in/foo.c:14:2: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
  scanf("%d",&n);
  ^~~~~
/in/foo.c:14:2: warning: incompatible implicit declaration of built-in function 'scanf'
/in/foo.c:14:2: note: include '<stdio.h>' or provide a declaration of 'scanf'
/in/foo.c:19:10: warning: implicit declaration of function 'getchar' [-Wimplicit-function-declaration]
   char c=getchar();
          ^~~~~~~
/in/foo.c:29:3: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
   printf("%d ",a[s]);
   ^~~~~~
/in/foo.c:29:3: warning: incompatible implicit declaration of built-in function 'printf'
/in/foo.c:29:3: note: include '<stdio.h>' or provide a declaration of 'printf'