import java.awt.geom.Point2D;
import java.io.*;
import java.math.*;
import java.util.*;
import java.util.Map.*;







class Main {
	static class Data implements Comparable<Data> {
		int id;
		int count;
		@Override
		public int compareTo(Data o) {
			return o.count - this.count;
		}
		public Data(int a, int b) {
			id = a;
			count = b;
		}
		
	}

	public static void main(String[] args) {	
		//FastScanner sc = new FastScanner();
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int[][] st = new int[N][N];
		for(int i = 0; i < N; i++) {
			char[] in = sc.next().toCharArray();
			for(int j = 0; j < N; j++) {
				if(in[j] == '#') st[i][j] = -1;
				if(in[j] == 'o') st[i][j] = 1;
				if(in[j] == 'x') st[i][j] = 2;
			}
		}
		int ans = check(st,0,0);
		System.out.println(ans);
	}
	static int check(int[][] st, int i, int j) {
		if(i >= st.length) {
			int[] count = new int[st.length];
			for(int k = 0; k < st.length; k++) {
				for(int l = 0; l < st[k].length; l++) {
					if(st[k][l] == 1) count[k]++;
				}
			}
			Data[] dd = new Data[st.length];
			for(int k = 0; k < st.length; k++) {
				dd[k] = new Data(k,count[k]);
			}
			Arrays.sort(dd);
			int[] ck = new int[st.length];
			int sk = 1;
			for(int k = 0; k < st.length; k++) {
				for(int l = k; l < st.length; l++) {
					ck[dd[l].id] = sk;
					
					if(l + 1 < st.length && dd[l+1].count != dd[l].count) {
						k = l;
						break;
					}
				}
				sk++;
			}
			return ck[0];
		}
		if(j >= st[i].length) {
			return check(st,i+1,0);
		}
		if(st[i][j] != 0) return check(st,i,j+1);
		int ret = 2 << 27;
		st[i][j] = 1;
		st[j][i] = 2;
		ret = check(st,i,j+1);
		st[i][j] = 2;
		st[j][i] = 1;
		ret = Math.min(check(st,i,j+1), ret);
		st[i][j] = 0;
		st[j][i] = 0;
		
		return ret;
		
		
	}


	
	static class FastScanner {
	    private final InputStream in = System.in;
	    private final byte[] buffer = new byte[1024];
	    private int ptr = 0;
	    private int buflen = 0;
	    private boolean hasNextByte() {
	        if (ptr < buflen) {
	            return true;
	        }else{
	            ptr = 0;
	            try {
	                buflen = in.read(buffer);
	            } catch (IOException e) {
	                e.printStackTrace();
	            }
	            if (buflen <= 0) {
	                return false;
	            }
	        }
	        return true;
	    }
	    private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
	    private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
	    private void skipUnprintable() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;}
	    public boolean hasNext() { skipUnprintable(); return hasNextByte();}
	    public String next() {
	        if (!hasNext()) throw new NoSuchElementException();
	        StringBuilder sb = new StringBuilder();
	        int b = readByte();
	        while(isPrintableChar(b)) {
	            sb.appendCodePoint(b);
	            b = readByte();
	        }
	        return sb.toString();
	    }
	    public long nextLong() {
	        if (!hasNext()) throw new NoSuchElementException();
	        long n = 0;
	        boolean minus = false;
	        int b = readByte();
	        if (b == '-') {
	            minus = true;
	            b = readByte();
	        }
	        if (b < '0' || '9' < b) {
	            throw new NumberFormatException();
	        }
	        while(true){
	            if ('0' <= b && b <= '9') {
	                n *= 10;
	                n += b - '0';
	            }else if(b == -1 || !isPrintableChar(b)){
	                return minus ? -n : n;
	            }else{
	                throw new NumberFormatException();
	            }
	            b = readByte();
	        }
	    }
	    public int nextInt() {
	        if (!hasNext()) throw new NoSuchElementException();
	        int n = 0;
	        boolean minus = false;
	        int b = readByte();
	        if (b == '-') {
	            minus = true;
	            b = readByte();
	        }
	        if (b < '0' || '9' < b) {
	            throw new NumberFormatException();
	        }
	        while(true){
	            if ('0' <= b && b <= '9') {
	                n *= 10;
	                n += b - '0';
	            }else if(b == -1 || !isPrintableChar(b)){
	                return minus ? -n : n;
	            }else{
	                throw new NumberFormatException();
	            }
	            b = readByte();
	        }
	    }
	}
}