package main

import . "fmt"

func main() {
	var n,m int
	Scan(&n,&m)
	a:=make([]int,m)
	for ;n>0;n-- {
		var s string
		Scan(&s)
		for i,c:=range s {
			if c=='x' {
				a[i]++
			}
		}
	}
	for _,h:=range a {
		if h>n {
			n=h
		}
	}
	Println(n+1)
}