#include <iostream>

#include <string>

#include <cstring>

#include <cstdlib>

#include <cstdio>

#include <cmath>

#include <algorithm>

#include <stack>

using namespace std;

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

#define pf printf

#define sf scanf

#define debug printf("!/n")

#define INF 1000

#define MAX(a,b) a>b?a:b

#define blank pf("\n")

#define LL long long

char str[];

int main()

{

          int n,i,j;

          while(~sf("%d",&n))

          {

               int cnt = ;

               bool flag=false;

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

               {

                    char tmp[];

                    sf("%s",tmp);

                    if(tmp[]=='')

                    {

                              flag = true;

                              continue;

                    }

                    if(tmp[]!='')

                    {

                              strcpy(str,tmp);

                              continue;

                    }

                    else

                    {

                              int len = strlen(tmp);

                              for(j = ;j<len;j++)

                              {

                                        if(tmp[j]!='')

                                        {

                                                  strcpy(str,tmp);

                                                  break;

                                        }

                                        cnt++;

                              }

                    }

               }

               if(flag)

               {

                    pf("0\n");

                    continue;

               }

               if(strlen(str)==)

               {

                    pf("1\n");

                    continue;

               }

               pf("%s",str);

               while(cnt--){pf("");}

               blank;

          }

          return ;

}