#include <bits/stdc++.h>
using namespace std;
const int Maxn = 1e6 + 1;
const int Mod = 1e9 + 7;
const long long int MOD = 1000000007LL;
const long long int MAX = 100010LL;
template <typename T>
T gcd(T a, T b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
template <typename T>
T power(T x, T y, long long int m = MOD) {
  T ans = 1;
  x %= m;
  while (y > 0) {
    if (y & 1ll) ans = (ans * x) % m;
    y >>= 1ll;
    x = (x * x) % m;
  }
  return ans % m;
}
template <typename T, typename T1>
T mod(T x, T1 p) {
  x %= p;
  if (x < 0) x += p;
  return x;
}
void leastPrimeFactor(vector<int> &least_prime, int n) {
  least_prime[1] = 1;
  for (int i = 2; i <= n; i++) {
    if (least_prime[i] == 0) {
      least_prime[i] = i;
      for (int j = 2 * i; j <= n; j += i)
        if (least_prime[j] == 0) least_prime[j] = i;
    }
  }
}
bool dfs(vector<vector<int>> &graph, vector<int> &g, int i) {
  int prev = 0;
  queue<int> q;
  q.push(i);
  while (!q.empty()) {
    int n = q.size();
    while (n--) {
      int t = q.front();
      q.pop();
      if (g[t] == -1) {
        g[t] = prev;
        for (int j : graph[t]) q.push(j);
      }
      if (g[t] != prev) return 0;
    }
    prev ^= 1;
  }
  return 1;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int n;
  cin >> n;
  vector<vector<int>> adj(n);
  vector<vector<int>> mat(n, vector<int>(n, 0));
  int cnt = n;
  for (int j = 0; j < n; j++) {
    string s;
    cin >> s;
    for (int i = 0; i < s.size(); i++)
      if (s[i] == '1') adj[j].push_back(i);
  }
  int m;
  cin >> m;
  vector<int> p(m);
  for (int i = 0; i < m; i++) cin >> p[i], p[i]--;
  for (int i = 0; i < n; i++) {
    queue<int> q;
    q.push(i);
    int dis = 0;
    vector<int> vis(n, 0);
    vis[i] = 1;
    while (!q.empty()) {
      int nu = q.size();
      while (nu--) {
        int no = q.front();
        q.pop();
        mat[i][no] = dis;
        for (int &ne : adj[no])
          if (!vis[ne]) vis[ne] = 1, q.push(ne);
      }
      dis++;
    }
  }
  vector<int> ans;
  ans.push_back(p[0]);
  int i = 0;
  while (i < p.size()) {
    int next = i + 1;
    for (int j = 0; j < n; j++)
      if (i + mat[p[i]][j] < p.size() && p[i + mat[p[i]][j]] == j)
        next = max(next, i + mat[p[i]][j]);
    if (next < p.size()) ans.push_back(p[next]);
    i = next;
  }
  cout << ans.size() << endl;
  for (int &i : ans) cout << i + 1 << " ";
  cout << endl;
}
