foo.c: In function 'main':
foo.c:9:33: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
    9 |  leap1=(year1%400==0||year1%4==0&&year1%100!=0);//2020年不是闰年
      |                       ~~~~~~~~~~^~~~~~~~~~~~~~
foo.c:10:33: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   10 |  leap2=(year2%400==0||year2%4==0&&year2%100!=0);
      |                       ~~~~~~~~~~^~~~~~~~~~~~~~
foo.c:5:38: warning: unused variable 'sum' [-Wunused-variable]
    5 |  int year1,month1,day1,i,leap1,leap2,sum=0;
      |                                      ^~~
foo.c:7:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    7 |  scanf("%d%d%d",&year1,&month1,&day1);
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.c:8:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    8 |  scanf("%d%d%d",&year2,&month2,&day2);
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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