#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

int q[10000][6],qb,qe,sx,sy,ex,ey,x,y,sn;
bool marked[10][10],found;

void put(int x,int y,int sn) {
    qe++;
    q[qe][1]=x; q[qe][2]=y; q[qe][3]=sn;
    //cout << x << " " << y << " " << sn << endl;
    marked[x][y]=true;
}

void get(int& x,int& y,int& sn) {
    x=q[qb][1]; y=q[qb][2]; sn=q[qb][3];
    qb++;
}

void startprocess() {
    string s,f;
    cin >> s >> f;
    sx=s[0]-'a'+1; sy=s[1]-'0';
    ex=f[0]-'a'+1; ey=f[1]-'0';
    for (int i=1;i<=8;i++)
        for (int j=1;j<=8;j++)
        marked[i][j]=false;

    found=false;
    put(sx,sy,0);
}

void putall(int x,int y,int sn,bool& found) {
    int h1=(sn+1)/2; int h2=sn/2;
    //cout << h1 << " " << h2 << endl;
    int steps[8][2] = {{h1,h2}, {h1,-h2}, {-h1,h2}, {-h1,-h2}, {h2,h1}, {h2,-h1}, {-h2,h1}, {-h2,-h1}};
    int i=0;
    while (i<8 && !found) {
        int cx=x+steps[i][0];
        int cy=y+steps[i][1];
        //cout << x << " " << y << " -> " << cx << " " << cy << " " << sn << endl;
        found=(cx==ex && cy==ey);
        if (cx>0 && cx<=8 && cy>0 && cy<=8)
            put(cx,cy,sn);
        i++;
    }
}

int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0);
    freopen("cheval.in","r",stdin);
    freopen("cheval.out","w",stdout);
    startprocess();
    while (qb<=qe && !found) {
        get(x,y,sn);
        sn++;
        if (sn>16) break;
        putall(x,y,sn,found);
    }
    if (!found) {
        cout << "-1";
    } else
        cout << sn;
}