foo.c: In function 'main':
foo.c:8:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d %d %d %d %d",&year1,&month1,&day1,&year2,&month2,&day2);
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.c:90:8: warning: 'days2' may be used uninitialized in this function [-Wmaybe-uninitialized]
   days2+=day2;
   ~~~~~^~~~~~
foo.c:54:8: warning: 'days1' may be used uninitialized in this function [-Wmaybe-uninitialized]
   days1+=day1;
   ~~~~~^~~~~~

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