#include <deque>
#include <iostream>
#include <string>
#include <queue>
#include <utility>
#include <vector>

using namespace std;

struct Graph {
    vector<vector<int>> graph;
    vector<bool> visited;
    vector<int> distances;
    queue<int> que;
    size_t start;
    size_t finish;
    size_t dist;

    explicit Graph(int n) : graph(n, vector<int>(n, 0)),
                            visited(n, false),
                            distances(n, 0),
                            start(0),
                            finish(0),
                            dist(0) {
        visited[start] = true;
        que.push(start);
    }

    void bfs();

};

void Graph::bfs() {
    while (!que.empty()) {
        int item = que.front();
        que.pop();
        for (size_t neig = 0; neig < graph.size(); ++neig) {
            if (graph[item][neig] == 1) {
                if (!visited[neig]) {
                    visited[neig] = true;
                    distances[neig] = distances[item] + 1;
                    que.push(neig);
                }
            }
        }
    }
}

int main() {
    int N;
    cin >> N;
    Graph g(N);
    for (int i = 0; i < N; ++i) {
        for (int j = 0; j < N; ++j) {
            int cell;
            cin >> cell;
            g.graph[i][j] = cell;
        }
    }
    int start;
    cin >> start;
    g.start = start - 1;
    int finish;
    cin >> finish;
    g.finish = finish - 1;
    g.bfs();
    if (g.distances[g.finish] == 0) {
        cout << -1;
    } else {
        cout << g.distances[g.finish];
    }
}