package main import ( "fmt" "math/rand" "time" ) func main() { var NUM, taro, jiro, taro_win int64 NUM = 200000 taro_win = 0 var N, K int64 fmt.Scan(&N, &K) NUM = NUM + 0 var i, j, k, l int64 for i=0; i<NUM; i++ { rand.Seed( time.Now().UnixNano()) taro = 0 jiro = 0 for j=0; j<N; j++ { jiro += int64(rand.Intn(6) + 1) } for k=0; k<K; k++ { taro += int64(rand.Intn(3)+4) } for l=0; l<N-K; l++ { taro += int64(rand.Intn(6) + 1) } if taro > jiro { taro_win += 1 } } fmt.Printf("%f", float64(taro_win)/float64(NUM)) }