to be at a loss;  to think and think but get nowhere;  to fail to come up with a good idea
 to be at a loss how to continue;  to become disheartened
 to think something over and over;  to rack one's brains;  to be at a loss
 to be at a loss;  to think and think but get nowhere;  to fail to come up with a good idea
 to be at a loss how to continue;  to become disheartened
 to think something over and over;  to rack one's brains;  to be at a loss