#include <stdio.h>
#include <assert.h>

#define MAX 100

int main () {
  int n,		      /* grau */
    i;			      /* n. de elementos vistos */
  double p[MAX+1],	      /* coeficientes do polinomio*/
    x0,			      /* ponto */
    pot, 		      /* x0^i */
    soma;		      /* aplicacao no ponto */
  
  scanf ( "%d", &n );	      /* le tamanho da sequencia */
  assert( n <= MAX );

  for ( i = 0; i <= n; i++ )  /* le cada coeficiente */
    scanf ( "%lf", &p[i] );	

  scanf ( "%lf", &x0 );	      /* le o ponto x0 */

  soma = 0; pot = 1;
  for ( i = 0; i <= n; i++ ) {
    soma = soma + p[i] * pot;
    pot = pot * x0;
  }

  printf("%g\n", soma);	      /* imprime resultado final */

  return 0;
}