I want to login to the dashboad but it shows this; Fatal

Hi,
I want to login to the dashboad but it shows this;

Fatal error: Allowed memory size of 41943040 bytes exhausted (tried to allocate 524288 bytes) in /home/kaisteve/public_html/kaiste1/wp-includes/compat.php on line 123

How can I solve this?

Regards