foo.cc: In function 'int main()':
foo.cc:31:22: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   if(y%400==0||y%4==0&&y%100!=0)
                ~~~~~~^~~~~~~~~~
foo.cc: In function 'int day(int, bool)':
foo.cc:21:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^
foo.cc: In function 'int main()':
foo.cc:12:4: warning: 'rn' may be used uninitialized in this function [-Wmaybe-uninitialized]
    if(rn)
    ^~
foo.cc:26:7: note: 'rn' was declared here
  bool rn;
       ^~

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