foo.c: In function 'main':
foo.c:8:13: warning: spurious trailing '%' in format [-Wformat=]
  printf("GUN%");
             ^
foo.c:9:14: warning: implicit declaration of function 'GUN' [-Wimplicit-function-declaration]
  printf("%s",GUN(n));
              ^~~
foo.c:9:11: warning: format '%s' expects argument of type 'char *', but argument 2 has type 'int' [-Wformat=]
  printf("%s",GUN(n));
          ~^  ~~~~~~
          %d
foo.c: In function 'GNU':
foo.c:12:9: warning: initialization makes integer from pointer without a cast [-Wint-conversion]
 {char a="isNotUnix";
         ^~~~~~~~~~~
foo.c:13:11: warning: format '%s' expects argument of type 'char *', but argument 2 has type 'int' [-Wformat=]
  printf("%s",a);
          ~^
          %d
foo.c:15:11: error: expected statement before ')' token
  return a;)
           ^
foo.c:15:11: error: expected declaration or statement at end of input
foo.c: In function 'main':
foo.c:7:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
  ^~~~~~~~~~~~~~

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