29번

#include<iostream>
#include<vector>

using namespace std;
int main() {
	int tmp = 0;
	int cnt = 0;
	int digit = 0;
	int N = 0;
	cin >> N;
	for (int i = 1; i <= N; i++)
	{
		tmp = i;
		while (tmp>0)
		{	
			if (tmp % 10 == 3)
			{
				cnt++;
			}
			tmp = tmp / 10;
		}
	}
	cout << cnt;
}