#include<bits/stdc++.h>
using namespace std;
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#define rep(i,n) for (int i=0;i<(long long)(n);i++)
#define all(v) v.begin(),v.end()
using ll=long long;
using pll=pair<ll,ll>;
using tll=tuple<ll,ll,ll>;
const ll INF=(1ll<<60);
template<class T> void chmin(T &a,T b){
    if(a>b){
        a=b;
    }
}
template<class T> void chmax(T &a,T b){
    if(a<b){
        a=b;
    }
}
int main(){
    ll n,k;
    cin >> n >> k;
    vector<vector<char>> s(n,vector<char>(k));
    rep(i,n){
        rep(j,k){
            cin >> s[i][j];
        }
    }
    vector<ll> v;
    rep(i,(1<<k)){
        vector<ll> p;
        rep(j,k){
            if(i&(1<<j)) p.push_back(j);
        }
        vector<ll> x(p.size());
        ll save=0;
        rep(j,n){
            if(j==0) continue;
            bool t=true;
            rep(l,p.size()){
                if(s[j][p[l]]<=s[save][p[l]]){
                    t=false;
                    break;
                }
            }
            if(t){
                save=j;
            }
        }
        v.push_back(save);
    }
    set<ll> ans;
    for(auto &i:v){
        rep(j,n){
            if(i==j) continue;
            bool t=true;
            rep(l,k){
                if(s[i][l]<s[j][l]){
                    t=false;
                    break;
                }
            }
            if(t) ans.insert(j);
        }
    }
    cout << ans.size() << endl;
}