/in/foo.c: In function 'main':
/in/foo.c:10:33: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
  leap1=(year1%400==0||year1%4==0&&year1%100!=0);//2020年不是闰年
                       ~~~~~~~~~~^~~~~~~~~~~~~~
/in/foo.c:11:33: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
  leap2=(year2%400==0||year2%4==0&&year2%100!=0);
                       ~~~~~~~~~~^~~~~~~~~~~~~~
/in/foo.c:39:32: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
     if(year1%400==0||year1%4==0&&year1%100!=0)//假设我不知道的情况下
                      ~~~~~~~~~~^~~~~~~~~~~~~~
/in/foo.c:54:25: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
      if(i%400==0||i%4==0&&i%100!=0)
                   ~~~~~~^~~~~~~~~~
/in/foo.c:6:38: warning: unused variable 'sum' [-Wunused-variable]
  int year1,month1,day1,i,leap1,leap2,sum=0;
                                      ^~~