一本通1095

//qf
#include<bits/stdc++.h>
#define f(i,j,n) for(register int i=j;i<=n;i++)
using namespace std;
typedef long long ll;
inline ll read(){
	ll x=0;
	int f=1;
	char ch=getchar();
	while(!isdigit(ch)) {
		if(ch=='-') f=-1;
		ch=getchar();
	}
	while(isdigit(ch)) x=(x<<1)+(x<<3)+ch-48,ch=getchar();
	return x*f;
}
ll n=read();
ll s=0;
signed main(){
	f(i,1,n){
		int j=i;
		while(j){
			if(j%10==1) s++;
			j/=10;
		}
	}
	cout<<s<<endl;
	return 0;
}