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

typedef long long ll;
typedef unsigned long long ull;
typedef __int128 i128;
typedef double db;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef pair<int,ll> pil;
typedef pair<ll,int> pli;
template <typename Type>
using vec=vector<Type>;
template <typename Type>
using grheap=priority_queue<Type>;
template <typename Type>
using lrheap=priority_queue<Type,vector<Type>,greater<Type> >;
#define fir first
#define sec second
#define pub push_back
#define pob pop_back
#define puf push_front
#define pof pop_front
#define chmax(a,b) a=max(a,b)
#define chmin(a,b) a=min(a,b)
#define rep(i,x,y) for(int i=x;i<=y;i++)
#define per(i,x,y) for(int i=y;i>=x;i--)

const int inf=0x3f3f3f3f;
const ll INF=0x3f3f3f3f3f3f3f3f;
const int mod=1e9+7/*998244353*/;

const int N=1e5+5,K=25;

int n,k;

bool vis[1<<21];
int dis[1<<21];

void print(int ans,int k){
    if(k>1)print(ans>>1,k-1);
    cout<<(ans&1);
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);cout.tie(0);
    cin>>n>>k;
    char c;int t;
    queue<int> q;
    rep(i,1,n){
        t=0;
        rep(j,1,k){
            cin>>c;
            t=t<<1|(c-'0');
        }
        q.push(t);
        vis[t]=true;
    }
    int ans=0;
    while(!q.empty()){
        int now=q.front();q.pop();
        rep(i,0,k-1){
            int nxt=now^1<<i;
            if(vis[nxt])continue;
            dis[nxt]=dis[now]+1;
            vis[nxt]=true;
            q.push(nxt);
            if(dis[nxt]>dis[ans])ans=nxt;
        }
    }
    print(ans,k);
    return 0;
}