/* -*- coding: utf-8 -*-
 *
 * 1908.cc:  No.1908 Assault for Keys - yukicoder
 */

#include<cstdio>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_N = 1000;
const int MAX_M = 1000;

/* typedef */

/* global variables */

char ss[MAX_N][MAX_M + 4];

/* subroutines */

/* main */

int main() {
  int n, m;
  scanf("%d%d", &n, &m);
  for (int i = 0; i < n; i++) scanf("%s", ss[i]);

  int maxc = 0;
  for (int j = 0; j < m; j++) {
    int cj = 0;
    for (int i = 0; i < n; i++)
      if (ss[i][j] == 'x') cj++;

    maxc = max(maxc, cj);
  }

  printf("%d\n", maxc + 1);
  return 0;
}