#include <iostream>
#include <vector>
#include <queue>

using namespace std;
vector<vector<int>> g;
queue<pair<int, int>> Q;
int di[8] = { -1,-2,-2,-1,1,2,2,1 };
int dj[8] = { -2,-1,1,2,2,1,-1,-2 };

void bfs()
{
	while (!Q.empty())
	{
		pair<int, int> cur = Q.front(); Q.pop();
		for (int i = 0; i < 8; i++)
		{
			int ni = cur.first + di[i]; int nj = cur.second + dj[i];
			if (ni > 0 && ni <= 8 && nj > 0 && nj <= 8)
			{
				if (g[ni][nj] > g[cur.first][cur.second] + 1)
				{
					Q.push({ ni,nj });
					g[ni][nj] = g[cur.first][cur.second] + 1;
				}
			}
		}
	}
}
int main()
{
	char a, b, c, d;
	cin >> a >> b >> c >> d;
	g.resize(9, vector<int>(9, 999999));
	int x1 = a - 'a' + 1, x2 = c - 'a' + 1, y1 = b - '0', y2 = d - '0';
	Q.push({ x1, y1 });
	g[x1][y1] = 0;
	bfs();
	if (!(g[x2][y2] & 1)) cout << g[x2][y2] / 2;
	else cout << -1;
	return 0;
}