#ifdef _WIN32
#  define LL "%I64d"
#else
#  define LL "%Ld"
#endif

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>
#include <ctime>
#include <vector>
#include <deque>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <bitset>
#include <string>
#include <algorithm>
#include <complex>
#include <utility>
#include <cassert>
using namespace std;
#define null NULL
#define mp make_pair
#define pb(a) push_back(a)
#define sz(a) ((int)(a).size())
#define all(a) a.begin() , a.end()
#define fi first
#define se second
#define relaxMin(a , b) (a) = min((a),(b))
#define relaxMax(a , b) (a) = max((a),(b))
#define SQR(a) ((a)*(a))
typedef vector<int> vi;
typedef pair<int,int> pii;
typedef long long ll;
#define INF 1000000000
int N;
int nxt[100010][10];
char buf[100];
int main(){
  freopen("numbers.in" , "r" , stdin);
  freopen("numbers.out" , "w" , stdout);
  scanf("%d" , &N);
  for(int i=0;i<=N;++i)
   for(int j=0;j<10;++j)
    nxt[i][j] = INF;
  for(int i=0;i<N;++i){
   scanf("%s" , &buf);
   int L = strlen(buf);
   for(int j=0;j<L;++j)
    nxt[i][buf[j] - '0'] = i;
                      }
  for(int i=N-1;i>=0;--i)
   for(int j=0;j<10;++j)
    relaxMin(nxt[i][j] , nxt[i+1][j]);
  int ANS = INF;
  for(int i=0;i<N;++i){
   int GO = i;
   for(int j=0;j<10;++j)
    relaxMax(GO , nxt[i][j]);
   if(GO - i + 1 > N) continue;
   relaxMin(ANS , GO - i + 1);
                      }
  if(ANS > N)puts("-1");
  else printf("%d\n" , ANS);
  return 0;
}