Problem:
Score : 1300 points

Problem Statement

There is a square-shaped grid with N vertical rows and N horizontal columns.
We will denote the square at the i-th row from the top and the j-th column from the left as (i,\ j).

Initially, each square is either white or black.
The initial color of the grid is given to you as characters a_{ij}, arranged in a square shape.
If the square (i,\ j) is white, a_{ij} is .. If it is black, a_{ij} is #.

You are developing a robot that repaints the grid.
It can repeatedly perform the following operation:

Select two integers i, j (1 ≤ i,\ j ≤ N). Memorize the colors of the squares (i,\ 1), (i,\ 2), ..., (i,\ N) as c_1, c_2, ..., c_N, respectively. Then, repaint the squares (1,\ j), (2,\ j), ..., (N,\ j) with the colors c_1, c_2, ..., c_N, respectively.

Your objective is to turn all the squares black.
Determine whether it is possible, and find the minimum necessary number of operations to achieve it if the answer is positive.

Constraints

2 ≤ N ≤ 500

a_{ij} is either . or #.

Partial Score

In a test set worth 300 points, N ≤ 3.

Input

The input is given from Standard Input in the following format:

N
a_{11}...a_{1N}
:
a_{N1}...a_{NN}

Output

If it is possible to turn all the squares black, print the minimum necessary number of operations to achieve the objective.
If it is impossible, print -1 instead.

Sample Input 1

2
#.
.#

Sample Output 1

3

For example, perform the operation as follows:

Select i = 1, j = 2.

Select i = 1, j = 1.

Select i = 1, j = 2.

The transition of the colors of the squares is shown in the figure below:

Sample Input 2

2
..
..

Sample Output 2

-1

Sample Input 3

2
##
##

Sample Output 3

0

Sample Input 4

3
.#.
###
.#.

Sample Output 4

2

Sample Input 5

3
...
.#.
...

Sample Output 5

5

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.io.*;
import java.util.*;

class Solver {
  final int n;
  final char[][] am;
  boolean[][] bm;
  
  Solver(int n, char[][] am) {
    this.n = n;
    this.am = am;
  }
  
  private int solveA(int i) {
    int countBlack = 0;
    for (int j = 0; j < n; j++) {
      if (bm[i][j]) {
        countBlack++;
      }
    }
    if (countBlack == 0) {
      return Integer.MAX_VALUE;
    }
    
    boolean hasBlack = false;
    for (int j = 0; j < n; j++) {
      if (bm[j][i]) {
        hasBlack = true;
      }
    }
    if (!hasBlack) {
      countBlack--;
    }
    
    int allBlackColumnCount = 0;
    for (int j = 0; j < n; j++) {
      boolean allBlack = true;
      for (int k = 0; k < n; k++) {
        if (!bm[k][j]) {
          allBlack = false;
          break;
        }
      }
      if (allBlack) {
        allBlackColumnCount++;
      }
    }
    return n - countBlack + n - allBlackColumnCount;
  }
  
  /*
  private int solveB(int i) {
    int countBlack = 0;
    for (int j = 0; j < n; j++) {
      if (bm[i][j]) {
        countBlack++;
      }
    }
    if (countBlack == 0) {
      return Integer.MAX_VALUE;
    }
    
    int copyCount = 0;
    for (int j = 0; j < n; j++) {
      boolean needCopy = false;
      for (int k = 0; k < n; k++) {
        if (bm[i][k] && !bm[j][k]) {
          needCopy = true;
          break;
        }
      }
      if (needCopy) {
        copyCount++;
      }
    }
    return n - countBlack + n - copyCount;
  }
  */
  
  
  public int solve() {
    bm = new boolean[n][n];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < n; j++) {
        bm[i][j] = am[i][j] == '#';
      }
    }
    
    int answer = Integer.MAX_VALUE;
    for (int i = 0; i < n; i++) {
      answer = Math.min(answer, solveA(i));
//      System.err.printf("%d: %d\n", i, solveA(i));
//      answer = Math.min(answer, solveB(i));
    }
    if (answer == Integer.MAX_VALUE) {
      return -1;
    }
    return answer;
  }
}

public class Main {
  private static void execute(ContestReader reader, PrintWriter out) {
    int n = reader.nextInt();
    char[][] am = reader.nextCharArray(n);
    out.println(new Solver(n, am).solve());
  }
  
  public static void main(String[] args) {
    ContestReader reader = new ContestReader(System.in);
    PrintWriter out = new PrintWriter(System.out);
    execute(reader, out);
    out.flush();
  }
}

class ContestReader {
  private BufferedReader reader;
  private StringTokenizer tokenizer;
  
  ContestReader(InputStream in) {
    reader = new BufferedReader(new InputStreamReader(in));
  }
  
  public String next() {
    while (tokenizer == null || !tokenizer.hasMoreTokens()) {
      try {
        tokenizer = new java.util.StringTokenizer(reader.readLine());
      } catch (Exception e) {
        throw new RuntimeException(e);
      }
    }
    return tokenizer.nextToken();
  }
  
  public int nextInt() {
    return Integer.parseInt(next());
  }
  
  public long nextLong() {
    return Long.parseLong(next());
  }
  
  public double nextDouble() {
    return Double.parseDouble(next());
  }
  
  public String[] next(int n) {
    String[] array = new String[n];
    for (int i = 0; i < n; i++) {
      array[i] = next();
    }
    return array;
  }
  
  public int[] nextInt(int n) {
    int[] array = new int[n];
    for (int i = 0; i < n; i++) {
      array[i] = nextInt();
    }
    return array;
  }
  
  public long[] nextLong(int n) {
    long[] array = new long[n];
    for (int i = 0; i < n; i++) {
      array[i] = nextLong();
    }
    return array;
  }
  
  public double[] nextDouble(int n) {
    double[] array = new double[n];
    for (int i = 0; i < n; i++) {
      array[i] = nextDouble();
    }
    return array;
  }
  
  public char[] nextCharArray() {
    return next().toCharArray();
  }
  
  public int[][] nextInt(int n, int m) {
    int[][] matrix = new int[n][m];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        matrix[i][j] = nextInt();
      }
    }
    return matrix;
  }
  
  public long[][] nextLong(int n, int m) {
    long[][] matrix = new long[n][m];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        matrix[i][j] = nextLong();
      }
    }
    return matrix;
  }
  
  public double[][] nextDouble(int n, int m) {
    double[][] matrix = new double[n][m];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        matrix[i][j] = nextDouble();
      }
    }
    return matrix;
  }
  
  public char[][] nextCharArray(int n) {
    char[][] matrix = new char[n][];
    for (int i = 0; i < n; i++) {
      matrix[i] = next().toCharArray();
    }
    return matrix;
  }
}