#include <iostream>

#include <cstdio>

#include <cstring>

#include <algorithm>

#include <climits>

#include <string.h>

#define LL __int64

using namespace std;

const int N=1<<16;

const int inf=1<<30;

int dp[N];

char str[25];

int ans[25];

int num[125],b,n,goal;

int judge(int f,int s){

	int tmp;int c=0;

	for(int k=0;k<b;k++){

		tmp=1<<k;

		if((f&tmp)==(s&tmp))

		c++;

	}

	return c;

}

int main(){

	while(scanf("%d%d",&b,&n)!=EOF){

		scanf("%s",str+1);

		goal=0;

		int len=strlen(str+1);

		for(int i=len;i>=1;i--){

			int t=str[i]-'0';

			goal+=t*(1<<(b-i));

		}

		int tmp=(1<<b)-1;;

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

			scanf("%s",str+1);

			len=strlen(str+1);

			num[k]=0;

			for(int i=len;i>=1;i--){

				int t=str[i]-'0';

				num[k]+=t*(1<<(b-i));

			}

		}

		bool flag=false;

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

			if(num[k]==goal){

				len=0;

				if(goal==0){

					printf("1\n");

					int pos=goal;

					while(b--){

						ans[++len]=pos%2;

						pos>>=1;

					}

					for(int i=len;i>0;i--)

					printf("%d",ans[i]);

					printf("\n");

					flag=true;

					break;

				}

				else if(goal!=0){

					printf("2\n");

					int pos=goal;

					while(b--){

						ans[++len]=pos%2;

						pos>>=1;

					}

					for(int i=len;i>0;i--)

					printf("%d",ans[i]);

					printf("\n");

					flag=true;

					break;

				}

			}

		}

		if(flag) continue;

		for(int k=0;k<=tmp;k++){

			dp[k]=inf;

		}

		for(int i=1;i<=n;i++)

		dp[num[i]]=0;

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

			for(int k=0;k<=tmp;k++){

				dp[k]=min(dp[k],dp[k^num[i]]+1);

			}

		}

		int pos=-1,c=-1,t;

		for(int k=0;k<=tmp;k++){

			if(dp[k]!=inf){

				t=judge(k,goal);

				if(t>c){

					pos=k;

					c=t;

				}

				else if(t==c){

					if(dp[pos]>dp[k])

					pos=k;

				}

			}

		}

		printf("%d\n",dp[pos]);

		len=0;

		while(b--){

			ans[++len]=pos%2;

			pos>>=1;

		}

		for(int i=len;i>0;i--)

		printf("%d",ans[i]);

		printf("\n");

	}

	return 0;

}