#include<math.h>
#include <stdio.h>

int n;
int a[1000024];
int count = 0;

int wtf(int i)
{
  count++;
  if (count >= 19997) {
    count -= 19997;
  }
  if (i == n - 1) {
    return a[i];
  }
  if (a[i] < wtf(i + 1)) {
    return a[i];
  } else {
    return wtf(i + 1);
  }
}

int main()
{
  FILE *fin = fopen("twoton.in", "r");
  FILE *fout = fopen("twoton.out", "w");
  fscanf(fin, "%d", &n);
  for (int i = 0; i < n; ++i) {
    fscanf(fin, "%d", &a[i]);
  }
  //wtf(0);
  count = pow(2, n) - 1;
  fprintf(fout, "%d\n", count);
  fclose(fin);
  fclose(fout);
}