#include<bits/stdc++.h>
using namespace std;
int a[20],t=0;
inline const void read(int *a)
{
	char c=getchar();
	while(c>='0'&&c<='9')
	{
		a[++t]=c-'0';
		c=getchar();
	}
}
int main()
{
	freopen("s.in.txt","r",stdin);
	read(a);
	a[t]--;
	int k=t;
	while(true)
	{
		if(a[k]<0)
		{
			a[k]+=10;
			a[k-1]--;
			k--;
		}
		else break;	
	}
	//cout<<"t="<<t<<endl;
	int l=1;
	while(!a[l]) l++;
	int r=l;
	while(r<=t)
	{
		a[r+1]+=10*(a[r]%2);
		a[r]=a[r]/2;
		r++;
	}
	bool w=false;
	//cout<<"l="<<l<<" t="<<t<<endl;
	for(int i=l;i<=t;i++)
	{//cout<<"*"<<endl;
		if(!w&&a[i])
		{
	    	w=true;
	    	cout<<a[i];
	    }
		else
		if(w)
		cout<<a[i];
	}
	cout<<endl;
	return 0;
}