Invalid input when i input #crypto isakmp key

Im trying to set up a VPN tunnel for router to router, however when i try and set the preshare key i recieve an invalid input statement. Any idea what this can be?

R1(config)#crypto isakmp policy 10 R1(config-isakmp)#hash md5 R1(config-isakmp)#authentication pre-share R1(config-isakmp)#crypto isakmp key ................. ^ % Invalid input detected at '^' marker.