import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.BufferedWriter;
import java.io.Writer;
import java.io.OutputStreamWriter;
import java.util.InputMismatchException;
import java.io.IOException;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author Egor Kulikov (egor@egork.net)
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        OutputWriter out = new OutputWriter(outputStream);
        TaskB solver = new TaskB();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskB {
        public void solve(int testNumber, InputReader in, OutputWriter out) {
            int n = in.readInt();
            char[][] map = IOUtils.readTable(in, n, n);
            int fill = n + 1;
            int special = n + 1;
            for (int i = 0; i < n; i++) {
                boolean has = false;
                for (int j = 0; j < n; j++) {
                    if (map[j][i] == '#') {
                        has = true;
                        break;
                    }
                }
                if (has) {
                    int current = 0;
                    for (int j = 0; j < n; j++) {
                        if (map[i][j] == '.') {
                            current++;
                        }
                    }
                    fill = Math.min(fill, current);
                } else {
                    int current = 0;
                    for (int j = 0; j < n; j++) {
                        if (map[i][j] == '.') {
                            current++;
                        }
                    }
                    special = Math.min(special, current);
                }
            }
            if (fill == n + 1) {
                out.printLine(-1);
                return;
            }
            fill = Math.min(fill, special + 1);
            int answer = fill;
            for (int i = 0; i < n; i++) {
                boolean good = true;
                for (int j = 0; j < n; j++) {
                    if (map[j][i] == '.') {
                        good = false;
                        break;
                    }
                }
                if (!good) {
                    answer++;
                }
            }
            out.printLine(answer);
        }

    }

    static class IOUtils {
        public static char[] readCharArray(InputReader in, int size) {
            char[] array = new char[size];
            for (int i = 0; i < size; i++) {
                array[i] = in.readCharacter();
            }
            return array;
        }

        public static char[][] readTable(InputReader in, int rowCount, int columnCount) {
            char[][] table = new char[rowCount][];
            for (int i = 0; i < rowCount; i++) {
                table[i] = readCharArray(in, columnCount);
            }
            return table;
        }

    }

    static class InputReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private InputReader.SpaceCharFilter filter;

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        public int read() {
            if (numChars == -1) {
                throw new InputMismatchException();
            }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        }

        public int readInt() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public boolean isSpaceChar(int c) {
            if (filter != null) {
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        }

        public static boolean isWhitespace(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public char readCharacter() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            return (char) c;
        }

        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);

        }

    }

    static class OutputWriter {
        private final PrintWriter writer;

        public OutputWriter(OutputStream outputStream) {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }

        public OutputWriter(Writer writer) {
            this.writer = new PrintWriter(writer);
        }

        public void close() {
            writer.close();
        }

        public void printLine(int i) {
            writer.println(i);
        }

    }
}



Measured memory_bytes: 22740