#include <bits/stdc++.h>

using namespace std;

int main()
{
	int n;
	scanf("%d", &n);
	vector <vector <int> > g(n, vector <int> (n));

	for (int i = 0; i < n; ++i)
		for (int j = 0; j < n; ++j)
			scanf("%d", &g[i][j]);

	int v_start, v_end;
	scanf("%d %d", &v_start, &v_end);
	v_start--;
	v_end--;

	queue <int> q;
	q.push(v_start);
	vector <bool> used(n, false);
	vector <int> dist(n, 0), prev(n);
	used[v_start] = true;
	prev[v_start] = -1;

	while (!q.empty())
	{
		int v = q.front();
		q.pop();

		for (int i = 0; i < n; ++i)
		{
			if (!used[i] && g[v][i] == 1)
			{
				used[i] = true;
				q.push(i);
				dist[i] = dist[v] + 1;
				prev[i] = v;
			}
		}

		used[v] = true;
	}

//	for (int i = 0; i < n; ++i)
//		printf("%d ", dist[i]);
//	printf("\n");
//	for (int i = 0; i < n; ++i)
//		printf("%d ", prev[i]);

	printf("%d", dist[v_end]);

	return 0;
}