#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cmath>

#define rep(i,n) for(i=0; i<n; ++i)
#define in(a) cin >> a
#define out(a,b) cout << a << b
using namespace std;
using lint = long long;

int main(void){
    int i, j;
    int n, m;
    in(n);
    in(m);
    vector<string> s(n);
    rep(i,n)    in(s[i]);
    int max=0;
    rep(j,m){
        int cnt=0;
        rep(i,n){
            cnt+=s[i][j]=='x';
        }
        if(cnt>max) max=cnt;
    }
    out(max+1,endl);
    return 0;
}