#include <vector>
#include <iostream>
using namespace std;

int fastest(vector <string> &A)
{
  vector <int> distance;
  vector <int> Q;
  int i, j, N;

  N = A.size();

  for (i = 0; i < N; i++) distance.push_back(-1);
  distance[0] = 0;
  Q.push_back(0);

  for (i = 0; i < Q.size(); i++) {
    if (Q[i] == N-1) return distance[N-1];
    for (j = 0; j < N; j++) {
      if (A[Q[i]][j] == '1' && distance[j] == -1) {
        distance[j] = distance[Q[i]]+1;
        Q.push_back(j);
      }
    }
  }
  return -1;
}

main()
{
  string s;
  int i, j;
  vector <string> A;

  while (cin >> s) A.push_back(s);
  for (i = 0; i < A.size(); i++) {
    if (A[i].size() != A.size()) { printf("Bad Input\n"); exit(0); }
    for (j = 0; j < A[i].size(); j++) if (A[i][j] != '0' && A[i][j] != '1') {
      printf("Bad Input\n"); 
      exit(0); 
    }
  }
  printf("%d\n", fastest(A));
}