// Bai Chem 6: Phan phong o (Tap the 2005)
#include<stdio.h>
#include<stdlib.h>
#define IN "ROOM.INP"
#define OUT "ROOM.OUT"
int *A,*B,n;
FILE *fin,*fout;
void ReadFile()
{
     fin=fopen(IN,"r");
     fscanf(fin,"%d",&n);
     // Cap phat bo nho dong
     A=(int*)malloc(n*sizeof(int));
     // Load Mang
     int i;
     for(i=0;i<n;i++) fscanf(fin,"%d",&A[i]);
     fclose(fin);
}
int Check(int j)
{
   for(int i=0;i<j;i++)
     if(B[j]==B[i]) return 0;
   return 1;
}
void Write(int tmp)
{
   fout=fopen(OUT,"w");
   fprintf(fout,"%d",tmp);
   fclose(fout);  
}
int main()
{
    ReadFile();
    int i,m=n,Flag=0;
    // Cho m tang tu n++, den khi thoa man
    do
    {
        int temp=m; 
        // Creat Arr phu
        B=(int*)malloc(n*sizeof(int));
        for(i=0;i<n;i++)
        {
            B[i]=A[i]%m;
            if(i && !Check(i))   
            {
                m++;
                free(B);
                break;                 
            }    
        }
        if (temp==m) Flag=1;
           
    }while(!Flag);
    free(A);
    Write(m);
}  
