#include <bits/stdc++.h>
#define ll long long
using namespace std;
string s,st="",ss;
string se(ll n, int len)
{
if(!len) return st ;
se(n>>1,len-1);
if( (n&1) ==1) return st+='7';
else return st+='4';
}
vector<ll> v;
int main()
{
bool t=0;
ios_base::sync_with_stdio(false);
ll x,y;
cin>>x;
for(int j=1;j<=9;j++){
for(ll i=0 ; i < (1<<j) ; i++){
ss=se(i,j);
v.push_back(atoi(ss.c_str()));
st="";
}
}
sort(v.begin(),v.end());
cout<<lower_bound(v.begin(),v.end(),x)-v.begin()+1<<endl;
return 0;
}
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