import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.Arrays;
import java.util.BitSet;
import java.util.StringTokenizer;

public class Main {
    public static void main(String[] args) {
        final BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        final BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        try {
            int T = 1;
            for (int i = 0; i < T; ++i) {
                Runner runner = new Runner(br, bw);
                runner.run();
                runner.flush();
            }
            br.close();
            bw.close();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
}

class Solution {
    int solution(int nRows, int nCols, boolean[][] board) {
        BitSet rows = new BitSet(nRows);
        BitSet cols = new BitSet(nCols);
        for (int i = 0; i < nRows; ++i) {
            for (int j = 0; j < nCols; ++j) {
                if (board[i][j]) {
                    rows.set(i);
                    cols.set(j);
                }
            }
        }
        return Math.max(nRows - rows.cardinality(), nCols - cols.cardinality());
    }
}

class Runner {
    final Reader reader;
    final BufferedWriter bw;

    final int nRows, nCols;
    final boolean[][] board;

    Runner(BufferedReader br, BufferedWriter bw) {
        this.reader = new Reader(br);
        this.bw = bw;
        try {
            var input = reader.readInts();
            this.nRows = input[0];
            this.nCols = input[1];
            this.board = new boolean[nRows][nCols];
            for (int i = 0; i < nRows; ++i) {
                String line = br.readLine();
                for (int j = 0; j < nCols; ++j) {
                    board[i][j] = line.charAt(j) == 'X';
                }
            }
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    public void flush() {
        try {
            bw.write('\n');
            bw.flush();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    public void run() throws IOException {
        var sol = new Solution();
        var res = sol.solution(nRows, nCols, board);
        bw.write(String.valueOf(res));
    }
}

class Reader {
    private BufferedReader br;

    public Reader(BufferedReader br) {
        this.br = br;
    }

    public int[] readInts() throws IOException {
        StringTokenizer st = new StringTokenizer(br.readLine(), " ");
        int cnt = st.countTokens();
        int[] ints = new int[cnt];
        for (int i = 0; i < cnt; ++i) {
            ints[i] = Integer.parseInt(st.nextToken());
        }
        return ints;
    }
}