foo.c: In function 'main':
foo.c:8:30: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   if(year%400==0||year%100!=0&&year%4==0) printf("29");
                   ~~~~~~~~~~~^~~~~~~~~~~
foo.c:5:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d",&year,&month);
  ^~~~~~~~~~~~~~~~~~~~~~~~~~