import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Scanner;

public class Main implements Runnable { //Runnableを実装する
    public static void main(String[] args) {
        new Thread(null, new Main(), "", 16 * 1024 * 1024).start(); //16MBスタックを確保して実行
    }
	
	public void run() {
		Scanner sc=new Scanner(System.in);
		PrintWriter pw=new PrintWriter(System.out);
		int N=sc.nextInt();
		int M=sc.nextInt();
		int[] cnt=new int[M];
		for (int i=0;i<N;++i) {
			char[] cs=sc.next().toCharArray();
			for (int j=0;j<cs.length;++j) {
				if (cs[j]=='x') ++cnt[j];
			}
		}
		int ans=Arrays.stream(cnt).max().getAsInt()+1;
		pw.println(ans);
		pw.close();
		
	}	
	
	void tr(Object ... o) {System.out.println(Arrays.deepToString(o));}
}