/in/foo.cc: In function 'int main()':
/in/foo.cc:5:2: error: 'cin' was not declared in this scope
  cin>>y>>m;
  ^~~
/in/foo.cc:6:11: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
  if(y%4==0&&y%100!=0||y%400==0)
     ~~~~~~^~~~~~~~~~
/in/foo.cc:17:2: error: 'cout' was not declared in this scope
  cout<<day;
  ^~~~