/in/foo.cc: In function 'int main()':
/in/foo.cc:6:17: warning: variable 'day2' set but not used [-Wunused-but-set-variable]
  int day=0,day1,day2,day3,day4;
                 ^~~~
/in/foo.cc:6:22: warning: variable 'day3' set but not used [-Wunused-but-set-variable]
  int day=0,day1,day2,day3,day4;
                      ^~~~
/in/foo.cc:40:16: warning: 'day4' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<day-day1-day4-2;
        ~~~~~~~~^~~~~
/in/foo.cc:40:11: warning: 'day1' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<day-day1-day4-2;
        ~~~^~~~~