Codeforces Round 293 (Div. 2)
D
Ilya and Escalator
Codeforces
1700
原题
← CE →
翻译中…

Ilya got tired of sports programming, left university and got a job in the subway. He was given the task to determine the escalator load factor.

翻译中…

Let's assume that $*n*$ people stand in the queue for the escalator. At each second one of the two following possibilities takes place: either the first person in the queue enters the escalator with probability $*p*$, or the first person in the queue doesn't move with probability $(1 - *p*)$, paralyzed by his fear of escalators and making the whole queue wait behind him.

翻译中…

Formally speaking, the $*i*$-th person in the queue cannot enter the escalator until people with indices from $1$ to $*i* - 1$ inclusive enter it. In one second only one person can enter the escalator. The escalator is infinite, so if a person enters it, he never leaves it, that is he will be standing on the escalator at any following second. Ilya needs to count the expected value of the number of people standing on the escalator after $*t*$ seconds.

翻译中…

Your task is to help him solve this complicated task.

翻译中…

Input

翻译中…

The first line of the input contains three numbers $*n*, *p*, *t*$ ($1 ≤ *n*, *t* ≤ 2000$, $0 ≤ *p* ≤ 1$). Numbers $*n*$ and $*t*$ are integers, number $*p*$ is real, given with exactly two digits after the decimal point.

翻译中…

Output

翻译中…

Print a single real number — the expected number of people who will be standing on the escalator after $*t*$ seconds. The absolute or relative error mustn't exceed $10^{ - 6}$.

翻译中…

样例

Input #1
1 0.50 1
Output #1
0.5
InputCopy OutputCopy
Input #2
1 0.50 4
Output #2
0.9375
InputCopy OutputCopy
Input #3
4 0.20 2
Output #3
0.4
InputCopy OutputCopy
题目信息
题号
518D
时间限制
2 s
内存限制
256 MB
标签
组合数学
动态规划
数学
概率论

题面与样例版权归 Codeforces 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。