/in/foo.cc:3:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main()
      ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:8:18: warning: suggest parentheses around comparison in operand of '&' [-Wparentheses]
  if(y%4==0&&y&100!=0||y%400==0)
               ~~~^~~
/in/foo.cc:8:21: warning: 'and' of mutually exclusive equal-tests is always 0
  if(y%4==0&&y&100!=0||y%400==0)
                     ^~
/in/foo.cc:8:11: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
  if(y%4==0&&y&100!=0||y%400==0)
     ~~~~~~^~~~~~~~~~