/in/foo.cc: In function 'int main()':
/in/foo.cc:9:4: warning: statement has no effect [-Wunused-value]
  bb-1;
  ~~^~
/in/foo.cc:10:13: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
  if(aa%4==0 && aa%100!=0 || aa%400==0)
     ~~~~~~~~^~~~~~~~~~~~
/in/foo.cc:26:5: warning: statement has no effect [-Wunused-value]
   aa-1;
   ~~^~