문제
걷기 전에 동전을 던진 다음, 앞 면이면 왼쪽으로 한 칸, 뒷 면이면 오른쪽으로 한 칸 이동하는 방법을 랜덤 걷기라고 한다. 이 랜덤 걷기의 위치의 기댓값은 항상 0이 된다. 즉, 랜덤 걷기를 아무리 많이 한다고 해도, 평균 위치는 처음 시작한 지점과 같다.
랜덤 걷기에서 왼쪽으로 갈 확률과 오른쪽으로 갈 확률, 그리고 동전을 던지는 횟수가 주어졌을 때, 가장 오른쪽 위치의 기댓값을 구하는 프로그램을 작성하시오.
출력
각 테스트 케이스에 대해서, 가장 오른쪽 위치의 기댓값(평균)을 소수점 넷째 자리 까지 출력한다.
예제 출력 1
복사
0.5000
1.1875
1.4965
3.9995
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