백준 1065

#include <iostream>
#include <string>
#include <iomanip>
using namespace std;
int getCount(int n) {
	if (n < 100) return n;
	int n1, n2, n3;
	int count = 99;
	for (int i = 100; i <= n; i++)
	{
		n1 = i / 100;
		n3 = i % 10;
		n2 = (i - (n1 * 100 + n3)) / 10;
		if (n2 - n1 == n3 - n2) count++;
	}
	return count;
}
int main() {
	int n;
	cin >> n;
	cout<<getCount(n);
}