#include <iostream>
using namespace std;
int n, res;
void dfs(int u, int v)
{
if (u / v)
{
if (u <= n) res ++ ;
return;
}
dfs(u * 10 + 4, v);
dfs(u * 10 + 7, v);
}
int main()
{
cin >> n;
for (int i = 1; i <= n; i *= 10) dfs(0, i);
cout << res;
return 0;
}