def find_road_number(S):
    current_road = 1
    increment = 1
    for direction in S:
        if direction == 'L':
            current_road += increment
        else:  # direction == 'R'
            current_road += increment + 1
        increment = increment * 2
    return current_road

# ユーザーからの入力の代わりにテスト文字列を使う
S = "RLLRLRLRRRLRL"

# 結果を出力
print(find_road_number(S))