#include 

using namespace std;

int n, g[101][101], d[101], s, f;
bool used[101];
queue  q;

int main() {
    cin >> n;
    for (int i = 1; i <= n; ++i) {
        for (int j = 1; j <= n; ++j) {
            cin >> g[i][j];
        }
    }
    cin >> s >> f;
    
    used[s] = true;
    d[s] = 0;
    q.push(s);
    
    while (!q.empty()) {
        int v = q.front();
        q.pop();
        for (int to = 1; to <= n; ++to) {
            if (g[v][to] == 1 && !used[to]) {
                used[to] = true;
                d[to] = d[v] + 1;
                q.push(to);
            }
        }
    }
    
    if (!used[f]) {
        cout << -1;
    } else {
        cout << d[f];
    }
    
    return 0;
}