#include <iostream>
#include <vector>
#include <queue>
#include <cmath>
using namespace std;
int exchange (char);
    vector <vector <int> > massiv(401);
    vector <int> way(401,-1);
int BFS (int, int, int, vector <int> , vector <int>);

int main () {
    int i, n=8, j, begin, end,x1,x2,y1,y2;
    char x11,x22;

    cin >>x11>>y1>>x22>>y2;

    y1--;
    y2--;//x1--;
   // x2--;
    x1=exchange(x11);
    x2=exchange(x22);
    vector <int> check(n*n);
    vector <int> length(n*n, 401);
    for (i = 0; i < n*n; i++) check[i] = 0;

   massiv.resize(n*n);
    for (i = 0; i < n*n; i++) {
        massiv[i].resize(n*n);
        for (j = 0; j < n*n; j++)
        {
        massiv[i][j]=0;
        if((i/n-j/n==1)&&(i%n-j%n==2)) massiv[i][j]=1;
        if((i/n-j/n==1)&&(i%n-j%n==-2)) massiv[i][j]=1;
        if((i/n-j/n==-1)&&(i%n-j%n==2)) massiv[i][j]=1;
        if((i/n-j/n==-1)&&(i%n-j%n==-2)) massiv[i][j]=1;
        if((i/n-j/n==2)&&(i%n-j%n==1)) massiv[i][j]=1;
        if((i/n-j/n==2)&&(i%n-j%n==-1)) massiv[i][j]=1;
        if((i/n-j/n==-2)&&(i%n-j%n==-1)) massiv[i][j]=1;
        if((i/n-j/n==-2)&&(i%n-j%n==1)) massiv[i][j]=1;
        };
    }
 begin=x1*n+y1;
 end=x2*n+y2;
    //cin >> begin >> end;
    if ((x1==x2)&&(y1==y2)) {cout<<0; return 0;};
    int result = BFS(end, begin, n*n, check, length);
    //if (result==101) {cout<<-1; return 0;};
    if(result%2==0)
    cout << result/2<<endl;
    else cout<<-1<<endl;//cout<<x1+1<<" "<<y1+1<<endl;
    //while(begin!=end)
    //{
        //cout<<way[begin]/n+1<<" "<<way[begin]%n+1<<endl;
    //  begin=way[begin];
    //}

    return 0;
}

int BFS (int b, int e, int n, vector <int> check, vector <int> length) {

    queue <int> vertex;

    int i, cur;
    vertex.push(b);
    //way[b]=0;
    //way.push_back(e);
    length[b]=0;
    check[b]=1;
    while (!vertex.empty()) {
        cur = vertex.front();
        vertex.pop();

        for (int j = 0; j < n; j++) {
            if ((check[j]==0)&&(massiv[cur][j]==1)){
                length[j]=length[cur]+1;
                check[j] = 1;
                vertex.push(j);
                way[j]=cur;
            }
    }
}
return length[e];
}
 int exchange( char coor)
 {
    if (coor=='a') return 0;
    if (coor=='b') return 1;
    if (coor=='c') return 2;
    if (coor=='d') return 3;
    if (coor=='e') return 4;
    if (coor=='f') return 5;
    if (coor=='g') return 6;
    if (coor=='h') return 7;
 }