question: What is the highest score for candidate Mohsen Rezaee when  candidate mir-hossein mousavi  scored 837858 votes?
answer: SELECT MAX(mohsen_rezaee) FROM table_23390604_1 WHERE mir_hossein_mousavi = 837858
context: CREATE TABLE table_23390604_1 (mohsen_rezaee INTEGER, mir_hossein_mousavi VARCHAR)