/in/foo.cc: In function 'int main()':
/in/foo.cc:22:15: warning: statement has no effect [-Wunused-value]
 mark[a2/100%10];
 ~~~~~~~~~~~~~~^
/in/foo.cc:24:11: warning: statement has no effect [-Wunused-value]
 mark[a3%10];
 ~~~~~~~~~~^