#include <iostream>
#include <vector>
#include <algorithm>
#include <queue>
using namespace std;

int main()
{
    int n;
    cin>>n;
    vector<vector<int> >gm(n+1, vector<int>(n+1));
    for(int i = 1; i <= n; i++)
    {
        for(int j = 1; j <= n; j++)
        {
            int x;
            cin>>x;
            gm[i][j] = x;
        }
    }
    vector<vector<int> >g(n+1);
    for(int i = 1; i <= n; i++)
    {
        for(int j = 1; j <= n; j++)
        {
            if(gm[i][j] == 1)
            {
                g[i].push_back(j);
            }
        }
    }
    int s, k;
    cin>>s>>k;
    int undef = -1;
    vector<int>dist(n+1, undef);
    queue<int>q;
    q.push(s);
    dist[s] = 0;
    while(!q.empty())
    {
        int x = q.front();
        q.pop();
        for(auto u: g[x])
        {
            if(dist[u] == undef)
            {
                dist[u] = dist[x] + 1;
                q.push(u);
            }
        }
    }
    cout<<dist[k];

    return 0;
}