foo.c:4:30: error: unknown type name 'day_start'
    4 | int day_diff(int month_start,day_start,month_end,day_end)
      |                              ^~~~~~~~~
foo.c:4:40: error: unknown type name 'month_end'
    4 | int day_diff(int month_start,day_start,month_end,day_end)
      |                                        ^~~~~~~~~
foo.c:4:50: error: unknown type name 'day_end'
    4 | int day_diff(int month_start,day_start,month_end,day_end)
      |                                                  ^~~~~~~
foo.c: In function 'sain':
foo.c:17: error: expected '{' at end of input
foo.c:17: warning: control reaches end of non-void function [-Wreturn-type]

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