A dangerous game
Alex got into serious trouble. He owes to the Mafia N dollars, and the time of reckoning has almost come. Alex is well known about the dangers of late return of the debt, so he wants to collect N dollars at any cost.
However, at the moment he has only M dollars. Alex’s buddy, who learned about the problems suggested a game — but this time for money. Alex has K attempts to bet any amount from zero to the amount that he has a — not necessarily even a whole number. With probability of P % Alex gets bet double in volume, otherwise gets nothing. Alex does not care of how much money will remain, most importantly, to have N dollars to pay off. Alex, of course, trying to play good as he can. Find out what a chances that Alex will return his debt.
Limit
0 ≤ N ≤ 10^9
0 ≤ M ≤ 10^9
1 ≤ K ≤ 12
0 ≤ P ≤ 100
Input
The single line contains four integers: N, M, K and P .
Output
You should print a single number — probability to collect enough money. Print the answer with an absolute error of not more than 10 ^7.