#include <stdio.h>

#define MAX_POW 32768

double integral(int n, double a[], double x)
{
  int i;
  double result=0,mn=1;
  for(i=0;i<=n;i++)
  {
    mn*=x;
    result+=a[i]*mn/(i+1);
  }
  return result;
}

double a[MAX_POW+1];

int main(void)
{
  int n,i;
  double x;
  scanf("%d",&n);
  for (i=0;i<=n;i++)
    scanf("%lf",&a[i]);
  scanf("%lf",&x);
  printf("%a",integral(n,a,x));
  return 0;
}