#include<bits/stdc++.h>
#define file(F) freopen(#F".in","r",stdin),freopen(#F".out","w",stdout)
#define lowbit(x) ((x)&-(x))
#define ALL(x) (x).begin(),(x).end()
#define debug(...) fprintf(stderr,__VA_ARGS__)
#define popc(x) (__builtin_popcountll((x)))
#define abs(x) ((x)>=0?(x):-(x))
using namespace std;
using ll=long long;
using uint=uint32_t;
template<typename T>
inline bool Max(T &x,T y) { return std::less<T>()(x,y)&&(x=y,true); }
template<typename T>
inline bool Min(T &x,T y) { return std::less<T>()(y,x)&&(x=y,true); }
void Solve();
int n,m;
int d[1<<20];
signed main() {
#ifndef ONLINE_JUDGE
#endif
   cin.tie(nullptr)->sync_with_stdio(false);
   Solve();
}
void Solve() {
   cin>>n>>m;
   for(int i=1;i<=n;i++) {
      int st=0;
      for(int j=0;j<m;j++) {
         char ch; cin>>ch; st=st<<1|(ch=='1');
      }
      d[st]=1;
   }
   queue<int> q;
   for(int st=0;st<1<<m;st++) if(d[st]) q.emplace(st);
   int ans,val=0;
   while(!q.empty()) {
      auto st=q.front(); q.pop();
      if(Max(val,d[st])) ans=st;
      for(int i=0;i<m;i++) if(!d[st^1<<i])
         d[st^1<<i]=d[st]+1,q.emplace(st^1<<i);
   }
   for(int i=m-1;~i;i--) putchar((ans>>i&1)+'0'); puts("");
}