#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define rep(i, n) for(int i = 0; i < n; i++)
#define repr(i, n) for(int i = n; i >= 0; i--)
#define range(i, m, n) for(int i = m; i < n; i++)
#define ALL(v) v.begin(), v.end()
#define RALL(v) v.rbegin(), v.rend()
#define sum(v) accumulate(ALL(v),0)
#define int long long
typedef long long ll;
typedef vector<ll> vl;
typedef vector<vector<ll>> vvl;
const ll MOD = 1000000007;
const ll MOD2 = 998244353;
const ll INF = 1e16;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
int SN(char s){return int32_t(s-'0');}
int SN(string s){return stoi(s);}
using Graph = vector<vector<ll>>;
int32_t main(){
    int N,M;cin >> N >> M;
    vector<string> S(N,"");
    rep(i,N)cin >> S[i];
    vvl Snum(N,vl(M,0));
    rep(i,N){
        rep(j,M){
            if(S[i][j]=='x'){
                Snum[i][j]=1;
            }
        }
    }
    int Ans;Ans = 0;
    rep(j,M){
        int tmp = 0;
        rep(i,N){
            tmp+=Snum[i][j];
        }
        Ans = max(Ans,tmp);
    }
    cout << Ans+1 << endl;
}