n = input()
l = ''
for i in n:
if i=='0':
l +='0'
elif i=='1':
l+='1'
else:
break
l+='1'*(len(n)-len(l))
print(int(l,2))#include <bits/stdc++.h>
using namespace std;
#define fast ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
const long int N=1e6;
int main()
{
fast;
string n;
cin>>n;
long long int som=0;
vector<long long int>dp(n.length());
dp[0]=1;
for(long long int i(1);i<(n.length());i++){
dp[i]=dp[i-1];
dp[i]*=2;}
for(long long int i(0);i<(n.length());i++){
som+=dp[i];}
bool test=true;
for(long long int i(0);i<(n.length()-1);i++){
if(n[i]>'1'){test=false;break;}
if(n[i]=='0'){
som-=dp[n.length()-1]/dp[i];}}
if(test!=false){
if(n[n.length()-1]=='0'){
som-=1;}}
cout<<som<<endl;
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