arr = []
def solve(n, num, index):
if n <= num:
arr.append(n)
elif n > num:
return
solve((n * 10) + 4, num, index + 1)
solve((n * 10) + 7, num, index + 1)
a = int(input())
solve(0, a, 0)
print(len(arr)-1)
#include<iostream>
#include<algorithm>
#include<vector>
#include<string>
#include<math.h>
using namespace std;
int main()
{
long long l, i, x, sum, p;
string n;
while (cin >> n)
{
l = n.size(); sum = 0, x = 1;
for (i = l - 1; i >= 0; i--) {
if (n[i] == '7')
p = pow(2, x);
else
p = pow(2, x) - pow(2, x - 1);
x++;
sum += p;
}
cout << sum << endl;
}
return 0;
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