uva 10900

题意一直没看懂~~~~不过看懂了之后还是感觉挺好的

#include<cstdio>
#include<cstring>
#include<algorithm>
#define maxn 32
using namespace std;
int n;
double p[maxn],t;

void pre()
{
    p[]=;
    for(int i=;i<=;i++)
        p[i]=p[i-]*2.0;
}

double solve()
{
    double f=p[n];
    for(int i=n-;i>=;i--)
    {
        double eq=p[i]/f;
        if(eq<t)
            f=(+t)*f/2.0;
        else
            f=(eq-t)*p[i]/(-t)+(-eq)*(eq+)*f/(-t)/2.0;
    }
    return f;
}

int main()
{
    pre();
    while(scanf("%d%lf",&n,&t)&&n)
    {
        printf("%.3lf\n",solve());
    }
    return ;
}