#include "bits/stdc++.h"
using namespace std;

/* macro */
#define rep(i,a,b) for(int i=a;i<b;i++)
#define revrep(i,a,b) for(int i = a; i > b; i--)
#define int long long
#define exist(s,e) ((s).find(e)!=(s).end())
#define all(v) (v).begin(), (v).end()
#define each(s,itr) for(auto (itr) = s.begin(); (itr) != s.end(); (itr)++)
#define sum(v) accumulate(all(v), (0LL))
#define isin(a, b, c) (b <= a && a <= c)
#define println cout << "\n";
#define sz(v) (int)v.size()


/* alias */
template<class T> using vec = vector<T>;
typedef vector<int> vi;
typedef pair<int, int> pi;
typedef tuple<int, int, int> ti;

/* constant */
const int inf = 1LL << 62;
//const int mod = 1e9 + 7;
const int dx[8]={1,0,-1,0,-1,1,-1,1};
const int dy[8]={0,1,0,-1,-1,-1,1,1};
const string alphabet = "abcdefghijklmnopqrstuvwxyz";

/* io_method */
int input(){int tmp;cin >> tmp;return tmp;}
string raw_input(){string tmp;cin >> tmp;return tmp;}
template<class T> void printx(T n){cout << n;}
template<class T, class U> void printx(pair<T, U> p){cout << "(" << p.first << "," << p.second << ")";}
template<class T, class U, class V> void printx(tuple<T, U, V> t){cout << "{" << get<0>(t) << "," << get<1>(t) <<"," << get<2>(t) << "}" << endl;}
template<class T> void printx(vector<T> v){cout << "{";rep(i,0,v.size()){printx(v[i]);if(i != v.size()-1)printx(",");}cout << "}";}
template<class T> void print(T n){printx(n);cout << endl;}
template<class T> void print(set<T> s){cout << "{";each(s, e){if(e != s.begin()) printx(",");printx(*e);}cout << "}" << endl;}
template<class T, class U> void print(map<T, U> mp){cout << "{";each(mp, e){cout << "(" << e -> first << "," << e -> second << ")";}cout << "}" << endl;}


/* general_method */
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
template<class T>T cut(T &a, int l, int r){return T(a.begin()+l, a.begin()+r);}

/* main */
int n, m;
bool arr[500][500];
void in(){
    cin >> n >> m;
    rep(i,0,n){
        rep(j,0,m){
            char c; cin >> c;
            arr[i][j] = (c == '1');
        }
    }
}

int bf(){

    int ans = 0;
    
    rep(i,0,(1 << n)){
        bool ing[m]; memset(ing, false, sizeof(ing));
        int cnt = 0;
        rep(j,0,n){
            if(i & (1 << j)){
                cnt++;
                rep(k,0,m) ing[k] ^= arr[j][k];
            }
        }

        bool isok = true;
        rep(j,0,m) if(ing[j] & 1) isok = false;
        if(isok) chmax(ans, cnt);
    }

    return ans;


}


int dp(){

    vi cur(1 << m, -1); cur[0] = 0;
    vi nxt(1 << m, -1);

    rep(i,0,n){
        int tmp = 0;
        int base = 0;
        rep(j,0,m){
            tmp += (arr[i][j] << base);
            base++;
        }
        rep(i,0,1 << m){
            if(cur[i] >= 0){
                chmax(nxt[i], cur[i]);
                chmax(nxt[i ^ tmp], 1 + cur[i]);
            }
        }

        cur = nxt;
        nxt.assign(1 << m, -1);
    }

    return cur[0];

}

void solve(){

    while(true){
        in();

        if(n == 0 && m == 0) return;

        if(n <= m){
            print(bf());
        }else{
            print(dp());
        }

    }

}

signed main(){

    cin.tie(0);
    ios::sync_with_stdio(false);
    solve();
    
}


Measured memory_bytes: 35748