foo.c: In function 'main':
foo.c:7:11: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
  if(y%4==0&&y%100!=0||y%400==0)
     ~~~~~~^~~~~~~~~~
foo.c:5:18: warning: unused variable 'flag' [-Wunused-variable]
  int y,m,d,i,j=0,flag = 1;
                  ^~~~
foo.c:6:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d-%d-%d",&y,&m,&d);
  ^~~~~~~~~~~~~~~~~~~~~~~~~~

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