#include<bits/stdc++.h>
using namespace std;

vector<string> comb;

void rec (int n,int i,string s) {
	if (i == n) {
		comb.push_back(s);
		return;
	}
	rec(n,i + 1,s + '0');
	rec(n,i + 1,s + '1');
}

int main () {
	 ios::sync_with_stdio(false);
	 cin.tie(nullptr);
	 cout.tie(nullptr);
	 for (int i = 1; i <= 10; ++i) {
		 rec(i,0,"");
	 }
	 vector<long long> a;
	 for (string s : comb) {
		 //1 => 7
		 //0 => 4
		 //~ 101 => 747
		 long long x = 0;
		 for (int i = 0; i < (int) s.size(); ++i) {
			 if (s[i] == '1') {
				 x = x * 10 + 7;
			 } else {
				 x = x * 10 + 4;
			 }
		 }
		 a.push_back(x);
	 }
	 sort (a.begin(),a.end());
	 //~ for (int i = 0; i < 10; ++i) {
		 //~ cout << a[i] << ' ';
	 //~ }
	 int n;
	 cin >> n;
	 for (int i = 0; i < (int) a.size(); ++i) {
		 if (a[i] == n) {
			 cout << i + 1 << '\n';
			 return 0;
		 }
	 }
}