foo.c: In function 'main':
foo.c:9:24: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   if(y1%400==0||y1%4==0&&y1%4!=0)
                 ~~~~~~~^~~~~~~~~
foo.c:5:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d%d",&y1,&m1,&d1);
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.c:6:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d%d",&y2,&m2,&d2);
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~

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