The Game

Struggling artist Min Hee-do is offered three billion won to bet his life if he loses a game against a rich old man, Kang No-sik, who is dying from a terminal illness. The game is for each man to dial a random phone number and guess if the person who answers will be male or female. Hee-do loses the bet, and after a month long brain operation wakes up to find that they have swapped bodies. (Wikipedia)