foo.c: In function 'main':
foo.c:16:17: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   if (a % 4 == 0&&a % 100 != 0||a % 400 == 0)
       ~~~~~~~~~~^~~~~~~~~~~~~~
foo.c:5:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d", &a,&b);
  ^~~~~~~~~~~~~~~~~~~~~

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