#include <iostream>
#include <vector>

using namespace std;
typedef vector <int> v_int;

int main()
{
	int n,k=0;
	v_int A;
	cin >> n;

		for(int i=0; i<n; i++)
		{
			A.push_back((i+k)%10);
			k=(i+k)/10;
		}

		for(int i=n; i<2*n; i++)
		{
			A.push_back((2*n-i+k)%10);
			k=(2*n-i+k)/10;
		}
		for(int i=A.size()-1; i>0; i--)
			cout << A[i];
}