using System;
using System.Linq;

public class Program
{
    private int N;
    private char[][] A;

    public void Solve()
    {
        var sc = new Scanner();
        N = sc.NextInt();
        A = new char[N][];
        for (int i = 0; i < N; i++)
        {
            A[i] = sc.Next().ToCharArray();
        }

        int[] rowCnt = new int[N];
        int[] columnCnt = new int[N];
        for (int i = 0; i < N; i++)
        {
            for (int j = 0; j < N; j++)
            {
                if (A[i][j] == '#')
                {
                    rowCnt[i]++;
                    columnCnt[j]++;
                }
            }
        }

        int maxRow = 0;

        for (int i = 0; i < N; i++)
        {
            maxRow = Math.Max(maxRow, rowCnt[i]);
        }

        if (maxRow == 0)
        {
            Console.WriteLine("-1");
            return;
        }

        int ans = 0;
        int t = int.MaxValue;
        for (int i = 0; i < N; i++)
        {
            int tmp;
            if (columnCnt[i] == 0)
            {
                tmp = N - rowCnt[i] + 1;
            }
            else
            {
                tmp = N - rowCnt[i];
            }

            t = Math.Min(t, tmp);
        }

        ans += t;

        for (int i = 0; i < N; i++)
        {
            if (columnCnt[i] < N)
                ans++;
        }
        Console.WriteLine(ans);
    }

    public static void Main(string[] args)
    {
        new Program().Solve();
    }
}

class Scanner
{
    public Scanner()
    {
        _pos = 0;
        _line = new string[0];
    }

    const char Separator = ' ';
    private int _pos;
    private string[] _line;

    #region スペース区切りで取得

    public string Next()
    {
        if (_pos >= _line.Length)
        {
            _line = Console.ReadLine().Split(Separator);
            _pos = 0;
        }

        return _line[_pos++];
    }

    public int NextInt()
    {
        return int.Parse(Next());
    }

    public long NextLong()
    {
        return long.Parse(Next());
    }

    public double NextDouble()
    {
        return double.Parse(Next());
    }

    #endregion

    #region 型変換

    private int[] ToIntArray(string[] array)
    {
        var result = new int[array.Length];
        for (int i = 0; i < array.Length; i++)
        {
            result[i] = int.Parse(array[i]);
        }

        return result;
    }

    private long[] ToLongArray(string[] array)
    {
        var result = new long[array.Length];
        for (int i = 0; i < array.Length; i++)
        {
            result[i] = long.Parse(array[i]);
        }

        return result;
    }

    private double[] ToDoubleArray(string[] array)
    {
        var result = new double[array.Length];
        for (int i = 0; i < array.Length; i++)
        {
            result[i] = double.Parse(array[i]);
        }

        return result;
    }

    #endregion

    #region 配列取得

    public string[] Array()
    {
        if (_pos >= _line.Length)
            _line = Console.ReadLine().Split(Separator);

        _pos = _line.Length;
        return _line;
    }

    public int[] IntArray()
    {
        return ToIntArray(Array());
    }

    public long[] LongArray()
    {
        return ToLongArray(Array());
    }

    public double[] DoubleArray()
    {
        return ToDoubleArray(Array());
    }

    #endregion
}

Measured memory_bytes: 13268