foo.c: In function 'DaysOfAMonth':
foo.c:6:24: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
    6 |         if (y % 4 == 0 && y % 100 != 0 || y % 400 == 0)
      |             ~~~~~~~~~~~^~~~~~~~~~~~~~~
foo.c: In function 'DaysOfAYear':
foo.c:13:22: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   13 |         return y%4==0&&y%100!=0||y%400==0?366:365;
      |                ~~~~~~^~~~~~~~~~
foo.c: In function 'main':
foo.c:19:32: error: 'res' undeclared (first use in this function)
   19 |         int sum1=0,sum2=0,sum3;res=0;
      |                                ^~~
foo.c:19:32: note: each undeclared identifier is reported only once for each function it appears in
foo.c:27:27: error: too few arguments to function 'DaysOfAMonth'
   27 |                 sum2=sum2+DaysOfAMonth(i);
      |                           ^~~~~~~~~~~~
foo.c:3:5: note: declared here
    3 | int DaysOfAMonth(int y, int m)
      |     ^~~~~~~~~~~~
foo.c:31:27: error: too few arguments to function 'DaysOfAMonth'
   31 |                 sum3=sum2+DaysOfAMonth(i);
      |                           ^~~~~~~~~~~~
foo.c:3:5: note: declared here
    3 | int DaysOfAMonth(int y, int m)
      |     ^~~~~~~~~~~~

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