#include <stdio.h>
#include <math.h>
using namespace std;
 
int main()
{
    int n; //описание переменных
    double x;
    scanf("%d %lf",&n,&x); //ввод условий
    double sum=0;
    double degree=1;
    for(int i=1;i<=n;i++)
    {
        degree=degree*2; //вычисление степеней 2
        sum=sum+(x+cos(i*x))/degree; //вычисление суммы
    }
    printf("%4.2lf\n",sum);
 
    return 0;
}
 

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