[1065] 한수

#include <iostream>
using namespace std;
int main()
{
	int n, i, count;
	int a, b, c;
	cin >> n;
	if (n < 100)
		cout << n;
	else
	{
		count = 99;
		for (i = 100; i <= n; i++)
		{
			a = i / 100;
			b = (i / 10) % 10;
			c = i % 10;
			if ((a - b) == (b - c))
				count++;
		}
		cout << count;
	}
}