37 lines
738 B
C++
37 lines
738 B
C++
#include<stdio.h>
|
|
#include<stdlib.h>
|
|
#include<string.h>
|
|
#include<iostream>
|
|
using namespace std;
|
|
double ex[30+5]={0.0};
|
|
double mon[30+5]={0.0};
|
|
double t=0.0;
|
|
int n=0;
|
|
double bp=0.0;
|
|
int main()
|
|
{
|
|
mon[0]=1;
|
|
for(int i=1;i<=30;i++)
|
|
{
|
|
mon[i]=mon[i-1]*2;
|
|
}
|
|
while(scanf("%d%lf",&n,&t)!=EOF&&(n>0))
|
|
{
|
|
ex[n]=mon[n];
|
|
for(int i=n-1;i>=0;i--)
|
|
{
|
|
bp=mon[i]/ex[i+1];
|
|
if(bp<=t)
|
|
{
|
|
ex[i]=(1+t)/2 * ex[i+1];
|
|
}
|
|
else
|
|
{
|
|
ex[i]=(bp-t)/(1-t) * mon[i] + (1-bp)/(1-t) * (1+bp)/2 * ex[i+1];
|
|
}
|
|
}
|
|
printf("%.3lf\n",ex[0]);
|
|
}
|
|
return(0);
|
|
}
|