//BFS и алгоритм Дейкстры. Теория. Задача А.
#include <bits/stdc++.h>
using namespace std;
int n, start, finish;
vector < vector < int > > g;
vector < int > dist;
vector < int > from;
 
void Dijkstra() {
    dist.resize(n, 1e9 + 7);
    from.resize(n);
    from[start] = -1;
    dist[start] = 0;
    set < pair < int , int > > s;
    s.insert({0, start});
    while (!s.empty()) {
        auto c = *s.begin();
        s.erase(s.begin());
        int v = c.second;
        for (int i = 0; i < n; i++) {
            if (g[v][i]) {
                if (dist[i] > dist[v] + 1) {
                    s.erase({dist[i], i});
                    dist[i] = dist[v] + 1;
                    from[i] = v;
                    s.insert({dist[i], i});
                }
            }
        }
    }
}
 
int main() {
    cin >> n;
    g.resize(n, vector < int > (n));
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            cin >> g[i][j];
        }
    }
    cin >> start >> finish;
    start--; finish--;
    Dijkstra();
    cout << (dist[finish] == 1e9 + 7 ? -1 : dist[finish]);
    return 0;
}