foo.cc:3:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
    3 | main()
      |      ^
foo.cc: In function 'int main()':
foo.cc:9:9: warning: zero-length gnu_printf format string [-Wformat-zero-length]
    9 |  printf("");
      |         ^~
foo.cc:14:10: warning: too many arguments for format [-Wformat-extra-args]
   14 |   printf("even\n", x);
      |          ^~~~~~~~
foo.cc:17:10: warning: too many arguments for format [-Wformat-extra-args]
   17 |   printf("odd\n", x);
      |          ^~~~~~~
foo.cc:11:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   11 |  scanf("%d", &x);
      |  ~~~~~^~~~~~~~~~

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