import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.stream.IntStream;
import java.util.Arrays;
import java.util.Collection;
import java.io.IOException;
import java.io.Reader;
import java.util.OptionalInt;
import java.io.InputStreamReader;
import java.util.Queue;
import java.io.BufferedReader;
import java.util.ArrayDeque;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        MyInput in = new MyInput(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        BGraphPartition solver = new BGraphPartition();
        solver.solve(1, in, out);
        out.close();
    }

    static class BGraphPartition {
        int n;
        char[][] es;

        public void solve(int testNumber, MyInput in, PrintWriter out) {
            n = in.nextInt();
            es = new char[n][];
            for (int i = 0; i < n; i++) {
                es[i] = in.nextChars();
            }

            int ans = 0;
            int[] depth = new int[n];
            for (int i = 0; i < n; i++) {
                Queue<Integer> q = new ArrayDeque<>();
                q.add(i);
                Arrays.fill(depth, -1);
                depth[i] = 0;
                while (!q.isEmpty()) {
                    Queue<Integer> q2 = new ArrayDeque<>();
                    for (int v : q) {
                        for (int t = 0; t < n; t++) {
                            if (es[v][t] != '1') {
                                continue;
                            }
                            if (depth[t] >= 0 && depth[t] % 2 == depth[v] % 2) {
//                            dump(v, t, depth);
                                out.println(-1);
                                return;
                            }
                            if (depth[t] >= 0) {
                                continue;
                            }
                            depth[t] = depth[v] + 1;
                            q2.add(t);
                        }
                    }
                    q.clear();
                    q.addAll(q2);
                    q2.clear();
                }
                ans = Math.max(ans, Arrays.stream(depth).max().getAsInt());
            }
            out.println(ans + 1);
        }

    }

    static class MyInput {
        private final BufferedReader in;
        private static int pos;
        private static int readLen;
        private static final char[] buffer = new char[1024 * 8];
        private static char[] str = new char[500 * 8 * 2];
        private static boolean[] isDigit = new boolean[256];
        private static boolean[] isSpace = new boolean[256];
        private static boolean[] isLineSep = new boolean[256];

        static {
            for (int i = 0; i < 10; i++) {
                isDigit['0' + i] = true;
            }
            isDigit['-'] = true;
            isSpace[' '] = isSpace['\r'] = isSpace['\n'] = isSpace['\t'] = true;
            isLineSep['\r'] = isLineSep['\n'] = true;
        }

        public MyInput(InputStream is) {
            in = new BufferedReader(new InputStreamReader(is));
        }

        public int read() {
            if (pos >= readLen) {
                pos = 0;
                try {
                    readLen = in.read(buffer);
                } catch (IOException e) {
                    throw new RuntimeException();
                }
                if (readLen <= 0) {
                    throw new MyInput.EndOfFileRuntimeException();
                }
            }
            return buffer[pos++];
        }

        public int nextInt() {
            int len = 0;
            str[len++] = nextChar();
            len = reads(len, isSpace);
            int i = 0;
            int ret = 0;
            if (str[0] == '-') {
                i = 1;
            }
            for (; i < len; i++) ret = ret * 10 + str[i] - '0';
            if (str[0] == '-') {
                ret = -ret;
            }
            return ret;
        }

        public char nextChar() {
            while (true) {
                final int c = read();
                if (!isSpace[c]) {
                    return (char) c;
                }
            }
        }

        int reads(int len, boolean[] accept) {
            try {
                while (true) {
                    final int c = read();
                    if (accept[c]) {
                        break;
                    }
                    if (str.length == len) {
                        char[] rep = new char[str.length * 3 / 2];
                        System.arraycopy(str, 0, rep, 0, str.length);
                        str = rep;
                    }
                    str[len++] = (char) c;
                }
            } catch (MyInput.EndOfFileRuntimeException e) {
            }
            return len;
        }

        public char[] nextChars() {
            int len = 0;
            str[len++] = nextChar();
            len = reads(len, isSpace);
            return Arrays.copyOf(str, len);
        }

        static class EndOfFileRuntimeException extends RuntimeException {
        }

    }
}



Measured memory_bytes: 31096