SEOUL, South Korea — A champion Go player scored his first win over a Go-playing computer program on Sunday after losing three straight times in the ancient Chinese board game, saying he finally found weaknesses in the software. Lee Sedol’s victory over AlphaGo is a reminder that Google’s Go-playing program has room for improvement despite winning the first three matches in the best-of-five series and the $1 million prize, which will be donated to charity.