#include <iostream>
using namespace std;
int main()
{
	int a,b;
	cin >> a >> b;
	int sum = 0;
	int num = a + b / 10.0;
	while (true)
	{
		if (1.9 * sum == num) break;
		if (1.9 * sum < num) sum++;
		if (1.9 * sum > num) 
		{
			sum--;
			break;
		}
	}
	cout << sum;
	return 0;
}