/in/foo.c: In function 'main':
/in/foo.c:13:10: warning: format '%c' expects argument of type 'char *', but argument 2 has type 'char (*)[(sizetype)(n)]' [-Wformat=]
  scanf("%c", &a);
          ^
/in/foo.c:12:2: warning: 'n' is used uninitialized in this function [-Wuninitialized]
  char a[n];
  ^~~~