#pragma GCC target("avx")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
//#define __INCLUDE_ATCODER_LIB
//#define __INTERPRETER
#ifdef __INCLUDE_ATCODER_LIB
#include <atcoder/all>
using namespace atcoder;
#endif
using namespace std;
#define overload4(a, b, c, d, e, ...) e
#define rep1(a)          for(decltype(a) i = 0, i##_len = (a); i < i##_len; ++i)
#define rep2(i, a)       for(decltype(a) i = 0, i##_len = (a); i < i##_len; ++i)
#define rep3(i, a, b)    for(decltype(b) i = (a), i##_len = (b); i < i##_len; ++i)
#define rep4(i, a, b, c) for(decltype(b) i = (a), i##_len = (b); i < i##_len; i += (c))
#define rep(...) overload4(__VA_ARGS__, rep4, rep3, rep2, rep1)(__VA_ARGS__)
#define rrep1(a)          for(decltype(a) i = (a); i--;)
#define rrep2(i, a)       for(decltype(a) i = (a); i--;)
#define rrep3(i, a, b)    for(decltype(a) i = (b), i##_len = (a); i-- > i##_len;)
#define rrep4(i, a, b, c) for(decltype(a) i = (a)+((b)-(a)-1)/(c)*(c), i##_len = (a); i >= i##_len; i -= c)
#define rrep(...) overload4(__VA_ARGS__, rrep4, rrep3, rrep2, rrep1)(__VA_ARGS__)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(x) ((int)(x).size())
#define yes(s) cout << ((s)?"Yes":"No") << "\n";
#define bit(n) (1LL << ((int)(n)))
#define get1bit(x,n) (((x) >> (int)(n)) & 1)
#define INF ((1 << 30) - 1)
#define INFL (1LL << 60)
#define PRECISION std::setprecision(16)
#ifdef __INTERPRETER
#define NO_SYNC_STD
#define ENDL std::endl
#else
#define NO_SYNC_STD std::cin.tie(nullptr);ios::sync_with_stdio(false)
#define ENDL "\n"
#endif
#ifdef __LOCAL
#include <dump.hpp>
#define dump(...) DUMPOUT << "  " << string(#__VA_ARGS__) << ": " << "[" << to_string(__LINE__) << ":" << __FUNCTION__ << "]" << endl << "    ", dump_func(__VA_ARGS__)
#else
#define dump(...)
#endif
using ll=long long;using ld=long double;template<class T> using V=vector<T>;template<class T> using VV=vector<vector<T>>;template<class T> using PQ=priority_queue<T,V<T>,greater<T>>;
template<class T> istream &operator>>(istream &is,complex<T> &v){T x,y; is >> x >> y;v.real(x);v.imag(y);return is;}
template<class T> istream &operator>>(istream &is,V<T> &v){for(auto&& e:v)is >> e;return is;}
template<class T,class U> istream &operator>>(istream &is,pair<T,U> &v){is >> v.first >> v.second;return is;}
template<class T,size_t n> istream &operator>>(istream &is,array<T,n> &v){for(auto&& e:v)is >> e;return is;}
template<class... A> void print_rest(){cout << ENDL;}
template<class T,class... A> void print_rest(const T& first,const A&... rest){cout << " " << first;print_rest(rest...);}
template<class T,class... A> void print(const T& first,const A&... rest){cout << fixed << PRECISION << first;print_rest(rest...);}
template<class T,class... A> void die(const T& first,const A&... rest){cout << fixed << PRECISION << first;print_rest(rest...);exit(0);}
template<class T> inline string join(const T& v,string sep=" "){if(v.size() == 0)return "";stringstream ss;for(auto&& e:v)ss << sep << e;return ss.str().substr(sz(sep));}
V<string> split(const string &s,char sep=' ') {V<string> ret;stringstream ss(s);string buf;while(getline(ss,buf,sep))ret.push_back(buf);return ret;}
template<class T> inline string padding(const T& v,int length,char pad=' ',bool left=false){stringstream ss;ss << (left?std::left:std::right) << setw(length) << setfill(pad) << v;return ss.str();}
template<class T> V<T> make_vec(size_t n,T a){return V<T>(n,a);}
template<class... Ts> auto make_vec(size_t n,Ts... ts){return V<decltype(make_vec(ts...))>(n,make_vec(ts...));}
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;}
template<class T,class F> pair<T,T> binarysearch(T ng,T ok,T eps,F f,bool sign=false){while(abs(ng-ok)>eps){auto mid=ng+(ok-ng)/2;if(sign^f(mid)){ok=mid;}else{ng=mid;}}return{ng,ok};}
template<class T> constexpr T cdiv(T x,T y){return (x+y-1)/y;}
template<class T> constexpr bool between(T a,T x,T b){return(a<=x&&x<b);}
template<class T> inline int between_count(V<T>&a,T l,T r) {return lower_bound(all(a),r)-lower_bound(all(a),l);}
template<class T> inline int lower_index(V<T>&a,T x){return distance(a.begin(),lower_bound(all(a),x));}
template<class T> inline int upper_index(V<T>&a,T x){return distance(a.begin(),upper_bound(all(a),x));}
template<class T> constexpr T pos1d(T y,T x,T h,T w){assert(between(T(0),y,h));assert(between(T(0),x,w));return y*w+x;}
template<class T> constexpr pair<T,T> pos2d(T p,T h,T w){T y=p/w,x=p-y*w;assert(between(T(0),y,h));assert(between(T(0),x,w));return{y,x};}
constexpr ll modpow(ll x,ll n,ll m=1152921504606846976LL){ll ret=1;for(;n>0;x=x*x%m,n>>=1)if(n&1)ret=ret*x%m;return ret;}
constexpr ll keta(ll n, ll base = 10LL) {ll ret = 0; while(n > 0) {n /= base, ret++;} return ret;}
constexpr int pcnt(ll x) {return __builtin_popcountll(x);}
constexpr int flog(ll x) {return 63 - __builtin_clzll(x);}
constexpr int clog(ll x) {return (x==1LL)?0:(64-__builtin_clzll(x-1LL));}


struct Solver {
  void solve() {
    ll n, m; cin >> n >> m;
    V<int> cnt(m);
    int ans = 0;
    rep(i,n) rep(j,m) {
      char c; cin >> c;
      cnt[j] += (c == 'x');
      chmax(ans,cnt[j]);
    }
    print(ans+1);
  }
} solver;
signed main(void){NO_SYNC_STD;dump("");solver.solve();return 0;}