简简单单

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