foo.c: In function 'yfts':
foo.c:4:24: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
    4 |         if (y % 4 == 0 && y % 100 != 0 || y % 400 == 0)
      |             ~~~~~~~~~~~^~~~~~~~~~~~~~~
foo.c: In function 'main':
foo.c:78:13: warning: unused variable 'i' [-Wunused-variable]
   78 |         int i = 0;
      |             ^
foo.c: In function 'yfts':
foo.c:72:1: warning: control reaches end of non-void function [-Wreturn-type]
   72 | }
      | ^

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