#include <bits/stdc++.h>
using namespace std;
using LL = long long;

#define fs first
#define sc second

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; }


// std::vector Declaration
template<typename T>
vector<T> make_v(size_t a) { return vector<T>(a); }
template<typename T,typename... Ts>
auto make_v(size_t a,Ts... ts) {
    return vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...));
}

// std::vector Initialization
template<typename T>
void fill_all(T& arr, const T& v) { arr = v; }
template<typename T, typename U>
void fill_all(T& arr, const U& v) { for (auto& i : arr) fill_all(i, v); }

// std::vector Debug
template<typename T>
ostream& operator<<(ostream& os, const vector<T>& v) {
    os << "[";
    bool a = 1;
    for (auto e : v ) {
        os << (a ? "" : " ");
        os << e;
        a = 0;
    }
    os << "]";
    return os;
}

// std::pair Debug
template<typename T, typename U>
ostream& operator<<(ostream& os, const pair<T, U>& p) {
    os << "(" << p.first << " " << p.second << ")";
    return os;
}

// std::set Debug
template<typename T>
ostream& operator<<(ostream& os, const set<T>& st) {
    os << "{";
    bool a = 1;
    for (auto e : st) {
        os << (a ? "" : " ");
        os << e;
        a = 0;
    }
    os << "}";
    return os;
}

// std::multiset Debug
template<typename T>
ostream& operator<<(ostream& os, const multiset<T>& st) {
    os << "{";
    bool a = 1;
    for (auto e : st) {
        os << (a ? "" : " ");
        os << e;
        a = 0;
    }
    os << "}";
    return os;
}

// std::map Debug
template<typename T, typename U>
ostream& operator<<(ostream& os, const map<T, U>& mp) {
    os << "{";
    bool a = 1;
    for (auto e : mp) {
        os << (a ? "" : " ");
        os << e.first << ":" << e.second;
        a = 0;
    }
    os << "}";
    return os;
}

// std::tuple Debug
template<int N, class Tuple>
void out(ostream& os, const Tuple& t){}
template<int N, class Tuple, class H, class ...Ts>
void out(ostream& os, const Tuple& t) {
    if (N) os << " ";
    os << get<N>(t);
    out<N+1,Tuple,Ts...>(os, t);
}
template<class ...Ts>
ostream& operator<<(ostream& os, const tuple<Ts...>& t) {
    os << "(";
    out<0,tuple<Ts...>,Ts...>(os, t);
    os << ")";
    return os;
}

// Debug
#define DUMP(x) cerr<<#x<<" = "<<(x)<<endl


struct edge { int to, cost; };
ostream& operator<<(ostream& os, const edge& e) {
    os << "(" << e.to << ", " << e.cost << ")";
    return os;
}

const LL LINF = 1LL<<60;
const int IINF = 1<<30;
const LL MOD = 1e9+7;

int main()
{

    vector<int> ns, ms;
    vector<vector<string>> bs;

    while (true) {
        int n, m; cin >> n >> m;

        if (n == 0 && m == 0) {
            break;
        }

        vector<string> b(n);
        for (int i = 0; i < n; ++i) {
            cin >> b[i];
        }

        ns.push_back(n);
        ms.push_back(m);
        bs.push_back(b);
    }

    for (int t = 0; t < ns.size(); ++t) {

        int n = ns[t], m = ms[t];
        vector<string> b = bs[t];

        if (m < n) {
            vector<int> c(n);
            for (int i = 0; i < n; ++i) {
                int s = 0;
                for (int j = 0; j < m; ++j) {
                    if (b[i][j] == '1') {
                        s |= 1<<j;
                    }
                }
                c[i] = s;
            }

            auto dp = make_v<int>(n+1, 1<<m);
            fill_all(dp, -1);
            for (int i = 0; i <= n; ++i) {
                dp[i][0] = 0;
            }


            for (int i = 0; i < n; ++i) {
                for (int s = 0; s < 1<<m; ++s) {
                    if (dp[i][s] != -1) {
                        chmax(dp[i+1][s], dp[i][s]);
                        chmax(dp[i+1][s ^ c[i]], dp[i][s]+1);
                    }
                }
            }

            cout << dp[n][0] << endl;
        }

        else {

            int ans = 0;

            vector<int> cnt(m);

            for (int s = 1; s < 1<<n; ++s) {

                int code = s ^ (s>>1);

                for (int i = 0; i < n; ++i) {
                    if (s >> i & 1) {
                        for (int j = 0; j < m; ++j) {
                            if (b[i][j] == '1') {
                                cnt[j] ^= 1;
                            }
                        }
                        break;
                    }
                }

                bool flag = true;
                for (int i = 0; i < m; ++i) {
                    if (cnt[i] != 0) {
                        flag = false;
                        break;
                    }
                }

                if (flag) {
                    int sz = 0;
                    for (int i = 0; i < n; ++i) {
                        if (code >> i & 1) {
                            ++sz;
                        }
                    }
                    chmax(ans, sz);
                }
            }

            cout << ans << endl;

        }
    }

    return 0;
}



Measured memory_bytes: 208508