#pragma GCC optimize(2)

#pragma GCC optimize(3)

#pragma GCC optimize(4)

#include<bits/stdc++.h>

using namespace std;

#define fi first

#define se second

#define pi acos(-1.0)

#define LL long long

//#define mp make_pair

#define pb push_back

#define ls rt<<1, l, m

#define rs rt<<1|1, m+1, r

#define ULL unsigned LL

#define pll pair<LL, LL>

#define pii pair<int, int>

#define piii pair<pii, int>

#define mem(a, b) memset(a, b, sizeof(a))

#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

#define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout);

//head

const int N = 1e5 + ;

queue<int> q;

int dis[N*];

int main() {

    fio;

    int n, k, ans;

    string s;

    cin >> n >> k;

    mem(dis, -);

    for (int i = ; i <= n; i++) {

        cin >> s;

        int now = ;

        for (int j = ; j < k; j++) if(s[j] == '') now |= <<j;

        q.push(now);

        dis[now] = ;

        ans = now;

    }

    int mx = ;

    while(!q.empty()) {

        int now = q.front();

        q.pop();

        for (int i = ; i < k; i++) {

            int nxt = now^(<<i);

            if(dis[nxt] == -) {

                dis[nxt] = dis[now] + ;

                q.push(nxt);

                if(dis[nxt] > mx) {

                    mx = dis[nxt];

                    ans = nxt;

                }

            }

        }

    }

    for (int i = ; i < k; i++) {

        if(ans & (<<i)) cout << ;

        else cout << ;

    }

    cout << endl;

    return ;

}