#include <stdio.h>
#include <algorithm>

using namespace std;

int make1(int number) {
  if (number == 0) return 4;
  int b[10], length = 0;
  while (number > 0) {
    int digit = number % 2;
    if (digit == 0) digit = 4;
    if (digit == 1) digit = 7;
    b[length++] = digit;
    number /= 2;
  }
  int result = 0;
  for (int i = 0, j = 1; i < length; i++, j *= 10) {
    result += b[i] * j;
  }
  return result;
}

int make2(int number) {
  int b[10], length = 0;
  while (number > 0) {
    int digit = number % 2;
    if (digit == 0) digit = 7;
    if (digit == 1) digit = 4;
    b[length++] = digit;
    number /= 2;
  }
  int result = 0;
  for (int i = 0, j = 1; i < length; i++, j *= 10) {
    result += b[i] * j;
  }
  return result;
}

int main() {
  int n, a[1234];
  for (int i = 0; i < 512; i++) {
    a[i] = make1(i);
  }
   for (int i = 1; i < 1024; i++) {
    a[i + 511] = make2(i + 1);
  }
  sort(a, a + 1024);
  scanf("%d", &n);
  for (int i = 0; i < 1024; i++) {
    if (a[i] == n) {
      printf("%d", i + 1);
      break;
    }
  }
  return 0;
}