#include<bits/stdc++.h>
using namespace std;
const int N = 2e5 + 6;
long long n,ans = 0;
int main(){
	scanf("%lld",&n);
	for (register long long i = 1;i <= n;++i){
		char a[N];
		snprintf(a,sizeof(a),"%lld",i);
		for (register long long j = 0;a[j] != '\0';++j){
			int ia = a[j] - '0';
			ans += ia;
		}
	}
	printf("%lld",ans);
	return 0;
}