#include <iostream>
using namespace std;
int main(){
int n,sum=0,a;
cin >> n ;
for(int i=1;i<=n;i++){
a = i;
while(a>0){
if (a % 10 == 1)
sum = sum + 1;
a = a / 10;
}
}
cout << sum << endl;
return 0;
}