/in/foo.cc: In function 'int main()':
/in/foo.cc:10:10: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
  if(r4==0&&r100!=0||r400==0) 
     ~~~~~^~~~~~~~~
/in/foo.cc:16:2: warning: this 'else' clause does not guard... [-Wmisleading-indentation]
  else
  ^~~~
/in/foo.cc:24:3: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'else'
   cout<<day; 
   ^~~~