#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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