foo.c: In function 'main':
foo.c:15:8: warning: statement with no effect [-Wunused-value]
   15 |    day:31;
      |        ^~
foo.c:26:16: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   26 |    if(year%4==0&&year%100!=0||year%400==0)
      |       ~~~~~~~~~^~~~~~~~~~~~~
foo.c:15:4: warning: label 'day' defined but not used [-Wunused-label]
   15 |    day:31;
      |    ^~~
foo.c:5:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    5 |  scanf("%d %d",&year,&month);
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~

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